编译：Karen
无论是对普通网络冲浪者还是网站管理员来说，Google都是目前世界范围内最受欢迎的搜索引擎。它每天处理的搜索请求高达1.5亿次，几乎占全球所有搜索量的1/3。网络冲浪者对Google情有独钟，是由于Google所提供的快速搜索速度及高命中率搜索结果。这些都是基于Google的复杂文本匹配运算法则及其搜索程序所使用的Pagerank™系统（网页级别技术）。下面我们将向大家介绍Google的Pagerank™系统。
Google之所以受网站管理员和Internet媒体服务公司的欢迎，是由于它并非只使用关键词或代理搜索技术，而是将自身建立在高级的网页级别技术基础之上。别的搜索引擎提供给搜索者的是多种渠道得来的一个粗略的搜索结果，而Google提供给它的搜索者的则是它自己产生的高度精确的搜索结果。这就是为什么网站管理员会千方百计去提高自己网站在Google的排名。
Google大受青睐的另一个原因就是它的网站索引速度。向Google提交你的网站直到为Google收录，一般只需两个星期。如果你的网站已经为Google收录，那么通常Google会每月一次遍历和更新(重新索引)你的网站信息。不过对于那些PR值(Pagerank)较高的网站，Google索引周期会相应的短一些。
Google的索引/重新索引周期比大多数搜索引擎要短。这就允许网站管理员可以对网站的页面属性进行编辑修改，如网页标题、头几行文字内容、大字标题、关键字分布，当然了还有外部链接的数量。然后他们很快就可以发现对网页所做的这些更改是否成功。
正因为Google如此受欢迎，你有必要知道Google的搜索引擎是如何工作的。如果不知道它是怎样决定你的排名，那么那些只是稍微熟悉Google排名运算法则的站点都会比你的排名位置要靠前。现在让我们来看一下Google的排名运算法则。
Google的排名运算法则主要使用了两个部分，第一个部分是它的文字内容匹配系统。Google使用该系统来发现与搜索者键入的搜索词相关的网页；第二部分也是排名运算法则中最最重要的部分，就是Google的专利网页级别技术（Pagerank™）。
我先来介绍一下如何使网站具有相关性，即文本内容匹配部分的运算法则：
在搜索网站的关键字时，Google会对其标题标签(meta title)中出现的关键字给予较高的权值。所以你应当确保在你网站的标题标签中包含了最重要的关键词，即应围绕你最重要的关键词来决定网页标题的内容。不过网页的标题不可过长，一般最好在35到40个字符之间。
众所周知，Google并不使用元标签(Meta Tags)如关键字或描述标签。这是由于在这些元标签中所使用的文字并不能为实际的访问者所看到。而且Google认为，这些元标签会被某些网站管理员用于欺诈性地放置一些与其网站毫不相干的热门关键词，并以此提高其网站对该不相干关键词的排名，从而以不正当的手段获得更多的访问者。
这种不支持Meta Tags的特性，意味着Google将从一个网页的头几行文字内容来生成对一个网站的描述。也就是说，你最好把你的关键字或关键短语放到网页的上方，这样如果Google找到它们，就会相应提高你网站的相关性。一旦Google找不到这样相关的内容，那么你要花费很大的力气来让你页面的其它部分具有相关性。
在决定一个网站的相关性时，Google也会考虑网页中正文内容的关键字密度(Keyword Density)，所以你要确保在你的整个网页中贯穿出现了若干次关键词和关键短语。但是要记住“过犹不及”，6-10%的关键词密度为最佳。
增加页面相关性的其它策略还包括：在
增加页面相关性的最后一个技巧就是使你网站上的外部文字链接包含你的关键字。在外部文字链接中包含关键字可有效提高你的网站相关性得分（Google在其PageRank技术的描述中，亦提及在计算网页级别时会对该网站的外部链接进行分析并计入相关性）。
在文字链接中应该包含多少关键字？这是个见仁见智的问题。不过我注意到有很多网站在他们的交换链接区域，已经提供了相应的文字链接内容。例如：“欢迎进行友情链接，并请使用如下代码建立至本网站的链接。”
上面我们介绍了Google如何计算网站的相关性，及如何增加网站相关性的一些有关知识。不过Google究竟使用什么方法来衡量一个网站的好坏呢？答案就是－Google的Pagerank™系统。
PageRank取自Google的创始人Larry Page，它是Google排名运算法则（排名公式）的一部分，用来标识网页的等级/重要性。级别从1到10级，10级为满分。PR值越高说明该网页越受欢迎（越重要）。例如：一个PR值为1的网站表明这个网站不太具有流行度，而PR值为7到10则表明这个网站非常受欢迎（或者说极其重要）。
在计算网站排名时，PageRank会将网站的外部链接数考虑进去。我们可以这样说：一个网站的外部链接数越多其PR值就越高；外部链接站点的级别越高（假如Macromedia的网站链到你的网站上），网站的PR值就越高。例如：如果ABC.COM网站上有一个XYZ.COM网站的链接，那么ABC.COM网站必须提供一些较好的网站内容，从而Google会把来自XYZ.COM的链接作为它对ABC.COM网站投的一票。你可以下载和安装Google的工具条来检查你的网站级别（PR值）。
那么是不是说，一个网站的外部链接数越高（获得的投票越多）， 这个网站就越重要，因而在用与其相关的关键词进行搜索时，它就会取得更高的排名呢？－－大错特错。
Google对一个网站上的外部链接数的重视程度并不意味着你因此可以不求策略地与任何网站建立连接。这是因为Google并不是简单地由计算网站的外部链接数来决定其等级。要是那样的话，所有网站管理员就只剩一件事情可做了－疯狂交换链接，尽可能获得最多的外部链接。Google是这样描述的：“Google不只是看一个网站的投票数量，或者这个网站的外部链接数量。同时，它也会对那些投票的网站进行分析。如果这些网站的PR值比较高（具有相当重要性），则其投票的网站可从中受益（亦具有重要性）。
那么，是不是说对一个网站而言，它所拥有的较高网站质量和较高PR分值的外部链接数量越多就越好呢？－也不尽然。
说它错是因为－Google的Pagerank系统不单考虑一个网站的外部链接质量，也会考虑其数量。比方说，对一个有一定PR值的网站X来说，如果你的网站Y是它的唯一一个外部链接，那么Google就相信网站X将你的网站Y视做它最好的一个外部链接，从而会给你的网站Y更多的分值。可是，如果网站X上已经有49个外部链接，那么Google就相信网站X只是将你的网站视做它第50个好的网站。因而你的外部链接站点上的外部链接数越多，你所能够得到的PR分值反而会越低，它们呈反比关系。
说它对是因为－一般情况下，一个PR分值大于等于6的外部链接站点，可显著提升你的PR分值。但如果这个外部链接站点已经有100个其它的外部链接时，那你能够得到的PR分值就几乎为零了。同样，如果一个外部链接站点的PR值仅为2，但你却是它的唯一一个外部链接，那么你所获得的PR值要远远大于那个PR值为6，外部链接数为100的网站。
这个问题现在看来好象越来越复杂了。不要紧，看看下面这个公式你就会完全理解了，只是需要一点数学知识。
首先让我们来解释一下什么是阻尼因数(damping factor)。阻尼因素就是当你投票或链接到另外一个站点时所获得的实际PR分值。阻尼因数一般是0.85。当然比起你网站的实际PR值，它就显得微不足道了。现在让我们来看看这个PR分值的计算公式：
PR(A) = (1-d) + d(PR(t1)/C(t1) + ... + PR(tn)/C(tn))
其中PR(A)表示的是从一个外部链接站点t1上，依据Pagerank™系统给你的网站所增加的PR分值；PR(t1)表示该外部链接网站本身的PR分值；C(t1)则表示该外部链接站点所拥有的外部链接数量。大家要谨记：一个网站的投票权值只有该网站PR分值的0.85，而且这个0.85的权值平均分配给其链接的每个外部网站。
设想一个名为akamarketing.com的网站，被链接至PR值为4，外部链接数为9的网站XYZ.COM，则计算公式如下：
PR(AKA) = (1-0.85) + 0.85*(4/10)
PR(AKA) = 0.15 + 0.85*(0.4)
PR(AKA) = 0.15 + 0.34
PR(AKA) = 0.49
也就是说，如果我的网站获得一个PR值为4，外部链接数为9的网站的链接，最后我的网站将获得0.49的PR分值。
再让我们看看如果我的网站获得的是一个PR分值为8，外部链接数为16的网站的链接，那么我将获得的PR分值将是：
PR(AKA) = (1-0.85) + 0.85*(8/16)
PR(AKA) = 0.15 + 0.85(0.5)
PR(AKA) = 0.15 + 0.425
PR(AKA) = 0.575
上述两个例子表明，外部链接站点的PR值固然重要，该站点的外部链接数也是一个需要考虑的重要因素。
好了，大家无须记住上面的公式，只要记住：在建设你自己网站的外部链接时，应尽可能找那些PR值高且外部链接数又少的网站。这样一来你网站上这样的外部链接站点越多，你的PR值就会越高，从而使得你的排名得到显著提升。
不过，为使你的PR值得到提高，你最应该做的一件事情就是－向DMOZ提交你的网站，从而为DMOZ，即ODP（开放目录专案）收录。
众所周知，Google的Pagerank™系统对那些门户网络目录如DMOZ，Yahoo和Looksmart尤为器重。特别是对DMOZ。一个网站上的DMOZ链接对Google的Pagerank™来说，就好象一块金子一样有价值。这时候收录该网站的那个DMOZ目录页的PR分值，也变得无足轻重了。我就看到过有一些站点，就因为被ODP所收录，从而身价倍增，其PR分值在Google上立即得到提升。这就是因为Google使用了它自己的ODP版本作为它的网站目录。
ODP的链接对Pagerank™非常重要。如果你的网站为ODP收录，则可有效提升你的页面等级。不信吗？
确实如此。在Google上随便找个词搜索，你会发现，Google所提供的搜索结果的头10个站点中，就有7到8个也同时在Google的目录中出现。这个事实足以说明，如果一个网站没有被ODP收录的话，那它也别指望能从Google上得到太多的访问量。
向ODP提交你的站点并为它收录，其实并不是一件难事，只是要多花点时间而已。只要确保你的网站提供了良好的内容，然后在ODP合适的目录下点击“增加站点”，按照提示一步步来就OK了。至少要保证你的索引页(INDEX PAGE)被收录进去。我说“至少”是因为尽管ODP声称他们只收录你的索引页，而事实上在ODP上却不乏被收录了5到10页的网站。所以，如果你的网站内容涉及完全不同的几块内容，你可以把每个内容的网页分别向ODP提交－不过请记住“欲速则不达”。等到Google对其目录更新后，你就能看到你的PR值会有什么变化了。
如果你的网站为Yahoo和Looksmart所收录，那么你的PR值会得到显著提升。关于“Yahoo提交技巧”，如果有时间可以阅读下面这篇文章“Yahoo网站提交技巧”。
如果你的网站是非商业性质的或几乎完全是非商业性质的内容，那么你可以通过www.Zeal.com使你的网站为著名的网络目录Looksmart所收录。我个人非常喜爱ZEAL.COM，就象Google也从DMOZ获得搜索结果一样，Looksmart也是从Zeal网络目录获得非商业搜索列表。
让我们继续－我是在一个星期二向Zeal提交的AKA Marketing.com，到了星期四早上它就出现在Zeal上了。到了星期一我检查了一下我的日志文件，发现来自Looksmart的大量提名，原来它已经被Looksmart收录了。后来我又查看了一下我的日志，发现MSN已经根据Looksmart的数据库而更新了它自己的数据库，而且由此而提升的好的排名也给我带来了不少的访问者。想想看吧，6天之内我的网站就出现在Zeal，Looksmart和MSN上了。所以如果你有非商业网站，可千万别忘了去Zeal.com提交你的网站哦！
在向Zeal.com提交你的网站前，你得先通过它的一个会员小测试。别担心，这个测试是很简单的。如果你是一个网站管理员，而你的网站又已经收录在三大知名网络目录DMOZ，Yahoo和Looksmart中，我猜想你的网站的PR值一定比较高，而且搜索排名也不会差。
综述：
1. 在网站的标题标签(TITLE tag)中包含主要关键词和关键短语。
2. 提高网站外部链接的质量和数量。
3. 使网站为三大知名网络目录DMOZ，Yahoo和Looksmart收录。
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Google Ranking Tips
by David Callan ?2003 http://www.akamarketing.com
Google is by far the most popular search engine available today for both ordinary surfers and webmasters.
Surfers like it because of the highly relevant results it gives, and the speed at which it delivers them. This is due to its complex text matching algorithm and of course the Pagerank system that this engine uses. More on the Pagerank system later.
Google is popular with webmasters and Internet Marketing companies due to the highly workable ranking system it uses.
Unlike other engines where information about how the results are obtained are sketchy at best, Google actually publishes information on its site about the results it produces. So webmasters have things they can do to produce higher rankings. What also makes Google popular with webmasters is the speed at which they will spider / list your site.
If you are not listed in Google and submit you're usually indexed within two weeks. If, however, your site is already listed in the index Google should re-index once every month, but more frequently if you have a high Pagerank and update often.
This indexing / re-indexing time is much quicker than most other search engines, this allows webmasters to edit their pages properties such as title, first few lines of text, headings, keyword distribution and of course the number of incoming links to their site. They can then discover quickly if the changes were successful or not.
It's because of this popularity that you need to know the workings of the Google search engine. Without knowledge of it you will be ranked lower than all other sites that are only slightly familiar with the Google algorithm.
So let's indulge ourselves in the Google ranking algorithm. Well, there are two main parts to the algorithm Google uses, the first is its text matching system, whereby Google tries to find pages relevant to what the searcher has entered. The second and equally important part of the algorithm is of course the Google patented Pagerank system.
I'll first go through how to make your page relevant, i.e. - the text matching part of the algorithm.
Google gives a lot of "weight" to the title tag when searching for keywords, so make sure your most important keywords or keyphrases appear in the title tag. It seems to work best if you have other words in your title tag, too, after your keywords, but try to remain under 35-40 characters.
As many of you know, Google does not use meta tags such as keywords or description tags. This is because the text in these tags cannot be seen by visitors to a website. Google therefore feels these tags will be abused by webmasters placing lots of unrelated words in them in order the get more visitors to their sites.
This lack of support for meta tags means that Google creates your description from the first few lines of text on your page, this means you've to have your keywords and phrases right at the top, if it finds them your page becomes more relevant. If it doesn't the rest of your page has to work harder to become relevant. For example have a look at http://www.akamarketing.com/google-ranking-tips.html. At the top of this page you will see:
AKA Marketing .com - Free Internet Marketing Articles , Google submitting tips, ranking high at google.com.
The above sentence includes keyphrases related to this page.
Google considers keyword density in the body of a page for determining relevancy too, so make sure your keywords and phrases appear a couple of times throughout the whole page. Don't go overboard though, a density of 6-10% seems to work best.
Other advice about making your page relevant includes putting keywords into the heading tags . Also try and bold as many keywords as you can. As of late Google seems to be indexing text in alt image tags, so include your keyphrases in there too.
One final tip on page relevancy is the point on having your keywords and phrases in links which point to your site. It is a good idea to have the linking text containing your keywords as Google even says itself that it analyzes pages that links come from too, in it's description of it's Pagerank technology.
How much keyword laden links matter is anyone's guess. I have noticed however a lot of sites which give the HTML code to visitors who want to exchange links do include keywords in theactual linking area. You should do something like this too on your links page, say something like "if you want to link to this site, please use the following code".
In the above section of the article you've learned what areas Google uses and looks at when looking for a relevant site. But what method does Google use to determine which site is better, the answer is the Pagerank system.
Pagerank is as the name suggests a ranking system of pages. It works on the basis that if a website ABC.COM has been linked from a website XYZ.COM, abc.com must have some good content and therefore Google will count the link from XYZ.COM as a vote for ABC.COM. You can check your link popularity on Google by downloading the Google toolbar from http://toolbar.google.com
The Pagerank scale goes from 1 to 10 on the Google toolbar and from 1 to 7 beside listings in the Google Directory. A less important site is of course a site with a PR of 1 and a very very important site is a site with a PR of 7 or 10, in the directory or toolbar respectively.
The more links or votes a site has the more important it must be and therefore the higher it will rank for search words which it is relevant to, right?, WRONG!.
Google does not simply count the number of incoming links a page has, if that was the case every webmaster from Iceland to Vietnam would try and exchange links to every Tom, Dick and Harry website that would let them. In Googles own words
"Google looks at more than the sheer volume of votes, or links a page receives; it also analyzes the page that casts the vote. Votes cast by pages that are themselves "important" weigh more heavily and help to make other pages "important."
Hopefully your beginning to get the idea. If not - The idea is to have your page linked to by as many high quality and high Pageranked sites as possible. Right?, RIGHT and WRONG.
WRONG BECAUSE - You see the Google Pagerank system also takes into account the number of links the page that has linked to you has. The reasoning for this is that a page X has a certain amount of voting PR, if your site Y is the only link from that page X, then Google feels confident that page X thinks your page Y is the best link it has, and will give you more PR. If however page X has 50 links, page X could think your only the 50th best page. So the more links it has the less of a PR boost your site gets.
RIGHT BECAUSE - Linking to a site with a 6+ PR will provide a significant boost to your PR in most cases, but in cases where the site also links with 100 other sites the boost will be almost zero. Likewise if a site has a PR of just 2 but you and only one other site are linked from it, then the PR boost would be more than the site with 100 links and a PR of 6.
It's beginning to come complex isn't it, just wait till you see this formula. Its looks scary for non math's people.
First let me explain what the damping factor is. The damping factor is the amount of your PR which you can actually pass on when you vote / link to another site. The damping factor is widely known to be .85. This is a little less then the linking pages own PR.
PR(A) = (1-d) + d(PR(t1)/C(t1) + ... + PR(tn)/C(tn))
In layman's terms PR(A) is the Pagerank boost your page will get after being linked from someone else's site (t1). PR(t1) is the Pagerank of the page which links to you and C(t1) is the amount of total links that (t1) has. It is important to know that a pages voting power is only .85 of that pages actual PR and this voting power gets spread out evenly between all sites it links to.
Imagine akamarketing.com was linked by XYZ.COM's link page which had a PR of 4 and 9 other links, here's how the formula should look like:
PR(AKA) = (1-.85) + .85*(4/10)
PR(AKA) = .15 + .85*(.4)
PR(AKA) = .15 + .34
PR(AKA) = .49
To sum up my site would get an injection of .49 PR after being linked from a page with a PR of 4 and 9 other links.
Lets say I was linked from a site with a PR of 8 - double the previous example's amount, which had 15 other links, a total of 16 outbound links, my boost would be:
PR(AKA) = (1-.85) +.85*(8/16)
PR(AKA) = .15 + .85(.5)
PR(AKA) = .15 + .425
PR(AKA) = .575
The above two worked examples show that not only is the PR of the linking page important but what is also important is how many other sites are also linked / voted for from that page.
OK, I think we've had enough mathy stuff for now, just remember that the name of the game is to get as many links from pages with high PR and few other links. The more of these links you get the more your PR will grow and the more your rankings will improve for your relevant keywords.
The best thing you can do for your PR at the moment seems to be getting your site listed in Dmoz.org - The Open Directory Project.
Pagerank is widely known to be biased towards big name directories such as Dmoz.org, Yahoo and Looksmart.
This is true, especially in the case of Dmoz.org. These ODP links are treated like gold by Pagerank. It doesn't even matter what the individual PR of the category page is. I have seen sites gain a large PR boost on the toolbar as soon as Google updates it's directory with the latest one from dmoz.org. This is because Google uses it's own version of ODP for the Google web directory.
Don't believe ODP links are very important to Pagerank? Don't believe a listing in the ODP will boost your ranking?
Well THEY ARE and IT WILL. Perform a search for almost anything on Google and you'll discover that 75-80% of the top 10 results are also indexed in the Google directory. The fact of the matter seems to me to be if your not listed in ODP, you shouldn't expect much traffic from Google.
It's not difficult, it does sometimes take time, but it's not difficult. Just make sure your site has good content and follow the guidelines for adding a URL. Try to get your index page listed at least. I say at least because although ODP claims only to list your index page, there are plenty of sites with 5 - 10 pages listed. So if your site has very distinctive sections, then submit each section - slowly. Once Google updates it's directory, these listings could do wonders for your sites maximum PR.
As for Yahoo and Looksmart, Pagerank will usually allocate a more than normal amount of PR boost for any sites listed. For tips on getting listed in Yahoo, read Yahoo Submitting Tips at http://www.akamarketing.com/Yahoo-submitting-tips.html
If you're a noncommercial site or have a site that's almost completely noncommercial you can get into the Looksmart directory through www.Zeal.com. I really love this site, just like Google obtains results from ODP, Looksmart obtains it's noncommercial listings from the Zeal web directory, without Zeal I would have to fork out hard earned cash and all my site does is provide information.
To continue - I submitted AKA Marketing.com on a Tuesday and was listed in Zeal by Thursday morning. On Monday I checked my logs and found lots of referrals from Looksmart, I was in Looksmart already. I looked at my logs later only to find MSN had updated it's database from the Looksmart database and was sending me loads of visitors because of the good listing I got. My site was listed in Zeal, Looksmart and MSN within six days. So get over to Zeal.com and submit your site.
Before you can submit a site however you must pass a member quiz, which is fairly simple and straightforward.
If you happen to be a webmaster that has a listing in all three of Dmoz.org, Yahoo and Looksmart then I'm guessing your site has good to very good PR and rankings.
RECAP
Have your main keywords and phrases in your TITLE tag and well spread throughout your page. Get as many links from as many high PR low number of outbound links pages you can. GET LISTED IN DMOZ.ORG, Yahoo and Looksmart.
Well that's it. I hope you have enjoyed reading this Google Ranking tips article has much as I have enjoyed writing it. I also hope that you can put this advice into use and help get yourself some real traffic.
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