Did you change any site settings recently?
You also might know that all folders should have 755 and all file should have 644 as permissions.Else errors occur. Read this and adjust settings accordingly.
You can revert back if the problem still persists.
No, I think I'm not changed any setting recently and last time I'm logged in,,
I'm facing this internal error about 12 hours ago, I don't think my .Htaccess is the source matter because I recoding it but the the prob still not fixed,,
Every my Web directory are set in 0755,, except the index file and any other file outside the directory are set in 0644,, should I changed it too ??
the strang things is, my subdomain seem to work fine,,http://ask.sinalfa.org although I'm not working on it yet. but my main site and mydomain.x10.mx are facing the same internal server error,, I'm not even touching mydomain.x10.mx it's still empty...