If you don't apply CSS to the Tabs then they will look like ordinary links overlapping each other. To make the Tabs look stylish you have put some cosmetics. The TabStrip control already has some built-in themes.

You can find the in-built CSS files at this location as you have already installed ComponentArt to your machine "C:\Program Files\ComponentArt\UI Framework 2010.1 for .NET\live_demos\aspnetajax\Common\themes\20101".

Inside each folder there is a CSS file. Add a reference for a particular file to your aspx page. Then set the AutoTheming property of the TabStrip Control to true. It will automatically apply the styles to the tabs. If you want some other style then you can create your own CSS and apply.