if you look at the whole line see below
Warning: 0 is not a MySQL result index in /home/etc/etc/etc/index2.php3 on line 25
it refers to you misreferencing a table, column name or db (typo whatever), the line number refers to where it is trying to pull result (mysql_fetch_array or whatever), check what sql query stmts for any typos and it should work fine for you. Basically it means it cant find anything and throws a wobbler :)
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cheers