More depth to the header

[Guest]

www.chinaindustrial.co.uk

 

you will see that the category tabs I have added to the header are behind the main body...how do I correct this or where is the depth of the cell/frame controlled...or is it the begining of these items that is set

 

sorry if this is realy obvious but it is years since I have worked on web pages when the frames were just introduced. My biggest problem is navigateing arround the site when looking at code >_<

 

thanks in advance Terence