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This subject particulary interests me because I am interested in developing a Web site which would by its nature contain very many links to pages found on external sites. I am now worried that my site would, in S.E.O. terms, be like a bucket with a hole in it!
Are my concerns justified?
[edited by: martinibuster at 10:08 pm (utc) on Aug. 22, 2004]
[edit reason] Edited for specifics [/edit]
The thing is, there are advantages to linking out to other pages. So you have to balance out the advantages and disadvatages. The best way to do that is to experiment and rea dthis board. Have fun doing both :)
a page with a PR of 5 links to two internal pages and one outbound link. That means that 2/3s of the pr goes to internal pages and 1/3 is 'leaked'.
The actual pages pr is NOT affected. But the PR wealth of your whole site may be reduced.
Outbound links are usually good for the user and is it is said to be now an important part of googles algo.
In short. Create your site for your users.
Build a structure that promotes good pr distribution but does not inhibit the purpose of the page.
therefore let us say for arguments sake that page1 has a pr of 3.
Now if page 1 links out to 3 sites the pr value of those links is split into 3. If it links out to 4 sites the pr is split up even more. Therefore a link to your site on a pr 4 page with 2 links is worth more than a link from a pr 5 page with a million links on it.
Now the value of the links going out from the page decrease with the number of links but page1's pr is not affected. page1's pr value is determined by what links to it NOT by what it links to- the value of the links from page1 to other pages is determined by page1's own pr and the number of links.
I probably didn't write that very well but end of story.
Oh and Gsmith just because it says "Full Member" next to my name doesn't mean I actually know anything. ;)
No. Pagerank is determined by what pages link to you.
And this includes pages on your own domain.
If you have a PR4 page... with three links off of it going to NASA, you will still have a PR4 page next update. If instead you have three links that go to other pages that link back to this PR4 page, this page will be PR4+ next update.
It's not complicated, even though people want to make it so. All your pages can cast votes. You can vote for pages that vote for you (either your own pages or something like a Yahoo category that links to you); or you can link to pages that in no way link to you, like linking to the Google main page.
If you do the latter instead of the former you will have a lower pagerank. That is the end of the story.
Linking to pages that in no way link back to you will result in you having lower pagerank compared to if you link to pages that do link back to you.
[edited by: Patrick_Taylor at 5:43 am (utc) on Aug. 23, 2004]
That is not how it works. Don't make something complex that is very simple.
If ten people vote for me, it just means that I now have a right to cast eight votes, while still having a value of ten myself.
George Bush was "elected" President via votes.
He appoints Cabinet Members (main subdirectory pages).
The Cabinet Members hire workers (individual html pages).
Nothing in this process lowered the power of the President.
Patrick Taylor I don't quite get what you're saying. Anyway the bottom line is:
Linking out does not affect your SERPS EXCEPT for when you are changing the number of links and you are also linking internally in which case those links would be worth less.
Yes of course but it doesn't entail that the original page loses some of it's PR merely because it links out. This only comes into play when we factor in where the linked-to pages themselves link out to and whether they link back to the original page or to pages 'near' it.
Patrick Taylor- You are incorrect.
I don't think so. The total amount of Google PR available throughout the web is created only by the presence of pages in Google's index. That total is not altered by links. Links in themselves do not create any additional total PR. They are simply a redistribution mechanism. This is how I understand it.
So it follows that a page must actually spend a proportion of its PR when it links to another. And 2 pages that link to each other are wasting whatever joint PR they have through the dampening factor.
I'm not commenting here on the merits or demerits of outgoing links - only on the fact that an outgoing link "per se" costs PR.
2.1 PageRank: Bringing Order to the Web
The citation (link) graph of the web is an important resource that has largely gone unused in existing web search engines. We have created maps containing as many as 518 million of these hyperlinks, a significant sample of the total. These maps allow rapid calculation of a web page's "PageRank", an objective measure of its citation importance that corresponds well with people's subjective idea of importance. Because of this correspondence, PageRank is an excellent way to prioritize the results of web keyword searches. For most popular subjects, a simple text matching search that is restricted to web page titles performs admirably when PageRank prioritizes the results (demo available at google.stanford.edu). For the type of full text searches in the main Google system, PageRank also helps a great deal.
2.1.1 Description of PageRank Calculation
Academic citation literature has been applied to the web, largely by counting citations or backlinks to a given page. This gives some approximation of a page's importance or quality. PageRank extends this idea by not counting links from all pages equally, and by normalizing by the number of links on a page. PageRank is defined as follows:
We assume page A has pages T1...Tn which point to it (i.e., are citations). The parameter d is a damping factor which can be set between 0 and 1. We usually set d to 0.85. There are more details about d in the next section. Also C(A) is defined as the number of links going out of page A. The PageRank of a page A is given as follows:
PR(A) = (1-d) + d (PR(T1)/C(T1) + ... + PR(Tn)/C(Tn))
Note that the PageRanks form a probability distribution over web pages, so the sum of all web pages' PageRanks will be one.
PageRank or PR(A) can be calculated using a simple iterative algorithm, and corresponds to the principal eigenvector of the normalized link matrix of the web. Also, a PageRank for 26 million web pages can be computed in a few hours on a medium size workstation. There are many other details which are beyond the scope of this paper.
2.1.2 Intuitive Justification
PageRank can be thought of as a model of user behavior. We assume there is a "random surfer" who is given a web page at random and keeps clicking on links, never hitting "back" but eventually gets bored and starts on another random page. The probability that the random surfer visits a page is its PageRank. And, the d damping factor is the probability at each page the "random surfer" will get bored and request another random page. One important variation is to only add the damping factor d to a single page, or a group of pages. This allows for personalization and can make it nearly impossible to deliberately mislead the system in order to get a higher ranking. We have several other extensions to PageRank, again see [Page 98].
Another intuitive justification is that a page can have a high PageRank if there are many pages that point to it, or if there are some pages that point to it and have a high PageRank. Intuitively, pages that are well cited from many places around the web are worth looking at. Also, pages that have perhaps only one citation from something like the Yahoo! homepage are also generally worth looking at. If a page was not high quality, or was a broken link, it is quite likely that Yahoo's homepage would not link to it. PageRank handles both these cases and everything in between by recursively propagating weights through the link structure of the web.
Ok so where does it say what you are saying?
1.case - increase of pr
if you link to pages which somehow (directly/indirectly) link back to you, will give you more pr in some cases.
2.case - decrease of pr
if you link to pages which never link back to you then you lower the pr that is passed to internal pages and pages that link back to your page, so you indeed are loosing pr on that page.
it is hard to say which outlinks can give you back pr, especially if it is passed indirectly. but if 2. is the case then you are really loosing pagerank, whereas the pagerank is not lowered by linking out but by passing pr to pages that will never pass it back to you. however, if you are trying to hoard pr then google might spot you as a pr hoarder and might punish you.
incorrect is that a page is loosing pr because an outlink is "costing" pr, correct is a page is loosing potential pr if an outlink never passes pr back directly or indirectly.
the total amount of pr is not determined by the total links on the web, but by the total pages. so additional outlinks do not affect anything but the pr a linked page is receiving and this can affect the linking page back.
deciding whether an outlink should happen or not is not a question of pagerank but of other things.
1. is it pointing to a bad neighbourhood
2. is it a useful page
an outlink MAY help you in the serps, though, but not many know how.
Clearly linking out to pages that do not link to you does "leak" PR from your site. Pagerank is calculated as the eigenvalues of a link matrix, which can be thought of as equivalent to a "random surfer" model, in which you imagine a hypothetical surfer clicking on random links -- where the surfer spends the most time has the most PR. Linking out sends the random surfer to some other page.
However, this does not mean linking out is bad. There are many factors in the algo, PR is only one. Google has said before that it is easy to spot a "PR hog," that is, a site which refuses to link out and is designed to hoard PR. Normal sites link out where appropriate. It has been speculated that links out to relevant pages may increase the relevance of a page, but I don't think this is known.
The bottom line here is that Google can tell a lot about your site from its linking patterns, and Google wants "natural" linking patterns. Google can be expected to get better and better at detecting this. So if your strategy is long-term, you should link out where appropriate to your users, that is, provide on-topic outbound links whenever you feel like it. The best way to "simulate" a natural link pattern is to just do whatever makes sense from a user perspective, that is, don't simulate it at all.