CSS Fix - 100% Hight Needed for PHPWcms CMS - Quick Fix

I require a quick fix within 1 hours - I have a fully designed template for PHPWcms CMS system which works fine aparts from the background image of the main container only displays to the height of the screen, if the content enterered into the CMS goes beyond the height of the screen the background image does not carry-on. Im sure this is a quick fix for a CSS expert but due to not having time to troubleshoot and needing this project completed by 5pm GMT today i need this fixing ASAP. Please only bid if you are sure you can fix it within an hour or so. Due to it been a quick fix, only a small budget for this.