Cannot post comments if I don’t post a website?

Try changing line 152 in your comments-template.php file from:

if ( empty( $url ) || 'http://' == $url )

to if ( empty( $url ) || 'http://' == $url || 'Website' == $url)

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)