I have check link in Yahoo, I found already 50 links to my site (see my signature) But Google indexed : 0 What is the reason ? Thanks
No it just doesn't display them all, use the webmaster tools on Google and you will see all your links.
Yes, Both Yahoo and Google updates the backlink index regularly but they choose to display them at different intervals (Google - quarterly etc). You should be able to see most of your backlinks known by Google in your Google Sitemap account before or during the next Google toolbar PR update in Apr.
There's another Google behavior that rarely gets mentioned when backlinks are discussed. Google is increasingly reluctant to crawl low-PR, cookie-cutter, link pages and automated link directories - far more so than either Yahoo! or MSN. Such pages are either never crawled at all, or crawled so infrequently that it can be months before they're counted. This is another reason why there's such a big difference in the way Google sees your links.
Google shows wrong # of backlinks if you use their url api ("link:") or use the functionality in their toolbar. This has been broken for years. You can use my tool to do that at Sheerseo dot com. You have 22 backlinks indexed by google.
is your site new ? you must wait , if your site is a new site and continue building link for your site
Google does not always show all their links, only a sample even though they are counting them and factoring them into their search algorithinms without your and public knowledge. Its a bit like their PR tool; although it updates all the time, for the public it updates every quarter or so.
It's weird I had a new site was on yahoo in days. Never got on google had to abondon site. Google really doesn't like duplicate content for what it is worth.
In the latest months this happens to me all the time. Yahoo seems pretty active, and show us the results sooner. Well, I don't stress much about this. I just write, and search engines will come.