Design Problem

Hi , i've just designed a js tab control . But there was a small design problem .

There's a horizon line which i want to remove (to make it look better) . My solution is using z-index and position to hide the line , but when i do that , the tab doesn't display correctly , it hides everything behind it .

Can you help me to fix it ? :)

you might get more responses if you post in the javascript forum:
http://codingforums.com/forumdisplay.php?f=2

Will

It's a Design Problem , not a javascript problem (it works correctly)

So i posted it here

Is there anyone help me plz ?