Well , if you want my advice, the secruity code is rubbish!
Why not get rid of it completly!

Go into your main directory of your site and find config.php

Open it in notepad and use notepad 'Find' to find the text $gfx_chk

It is normally set to $gfx_chk = 7;

If you want to remove it completly just replace the 7 with a 0