Error insertar mysql PHP

[DavidBL]

Tengo esto:

Código PHP:

$q = mysql_query("INSERT INTO 'usuarios'('key','email','password') VALUES($key,$email,$password)") or die(mysql_error());
 

y me da el siguiente error:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''usuarios'('key','email','password') VALUES(8,xxx,xxx' at line 1