People can easily come with sql-injections if you use that code.

You have to use for example mysql_real_escape_string or something else. Read about safety at php.net

first try (well apart from phpinfo; - thats basically phps hello world)

i already knew SQL SELECT statements and basic HTML so i got a book on PHP and after seeing generally how things were done, i decided to make thay

if you are still having the problem, in which line the error is being indicated?