How does Google decide what are valid backlinks?

[DesignsOnline]

I have just 7 backlinks according to google. But According to Yahoo there are over 40, I have added a link to my site in most of the websites I have built for people, but most of these dont get counted by Google. Also I use espotting.com and so my site is advertised on loads of websites at any one time. But these dont get picked up by google either. How can I raise my backlinks in Google and what does it require to count a link as a valid backlink?

Thanks

[TN Todd]

Google only updates it's backlinks periodically and it only shows backlinks from pages with a PR4 or higher.

[pcarlow]

The Google links command only shows a sample of the back links that Google knows about. Also, it use to primarly show only PR4 or greater links. That's not the case anymore. For example, the 7 back links Google shows for your site, are all under PR4. Google links command used to be much better than it is now. I personally don't even check it anymore. If I want to count links I use Yahoo.

[TechEvangelist]

Google has changed the way that it displays backlinks. It used to be that a backlink had to have a PR of 4 or better. I've got backlinks with PRs of 0 and 2 showing, and about 20 backlinks with a PR of 4 or 5 have disappeared.

Another forum mentioned a GoogleGuy statement that said Google is now displaying a random sample of backlinks. I have not seen the statement, but it shouldn't be hard to find.

[randfish]

Google has a very sophisticated formula for this -

They print out a big poster with all your links on it and place it in a big rate cage. Wherever the rats don't poop - those are the links they show.

[cbp]

This comes up so often, there is a stciky thread of it at the top of the Google forum:
http://www.webproworld.com/viewtopic.php?t=25934

Ignore what Google shows as backlinks - it is meaningless random sample. Just because a link is in the sample or not does not mean it is not counted for PR and ranking etc.

CBP

[AndrewX]

I think big G has made these modifications to make it harder for SEOs to game their system. Wouldn't it be nice to see a complete list of backlinks? That's because you are a webmaster with interest in your ranking and improving it. Regular Google users don't really need this functionality.

[greeneagle]

randfish:

"Google has a very sophisticated formula for this -

They print out a big poster with all your links on it and place it in a big rate cage. Wherever the rats don't poop - those are the links they show.
"
____

Please expound upon your knowledge here.

Thanks,
Ken

[clasione]

I believe Google has a random algo on which links show and which ones dont.... I'm only guessing but I imagine the most theamed links will show when they are on different IP ranges - filtering out site-wide links and none themed, but it should shift slightly between high and low PR links....

This will help to keep the seo professional confused by allowing a shifting algo-ever changing from high to low pr.

A guess, but an educated one.

[DrTandem1]

I suspect Google also has a time threshold before it counts the link. In other words, it may be that the link needs to be up for a certain amount of time.

Also, from what I have witnessed, it is taking sites about six months from the date of indexing to get a PR number.

[DesignsOnline]

In that case how long does it take to improve an existing PR number? (Especialy if it is fairly low like mine and just "4")