How can I prevent a WebPartZone from wrapping with
For web accessibility we don't want WebParts to be wrapped in tables.
To get rid of the HTML you can add a control adapter to your web part zone control.
Unfortunately my experience is that WebPartZone always renders those tables. If you want to conform to accessibility standards, you will have to ditch web part zones.
See the accessibility section at http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.webparts.webpartzone.aspx