WinKam

Or how can I improve searching in wordpress blog?

Yes, that was the problem. I removed it and now it works!

Thanks again!

Ipstenu, you was right!

This problem was because I was created a sub domain for this site! I deleted the sub domain and now the site works in normal sub folder style!

Thanks for the help!

I was wondering 2 days if this is an error from the current theme or something else inside the site!

I use subfolders now. I have 3 installed sites. The other 2 are working. This issue is happened for only 1 of them. And that is when i try to open index page and search page. The other pages in this site are working. I will check for a error in the theme. But I think is not in the theme!