Fix various compatibility bugs with old browsers.
Remove 2 unused images.
Cleaner way to draw tabs.
Use h6 instead of hr tag as a "clear: both" element.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@8184 20353a03-c40f-0410-a6d1-a30d3c3de9de