Hello,

I've checked the customization possibilities of the tab menu web part however, there is no easy way how to achieve this. The tab menu can't be customized to such extend as the CSS list menu, that's why I would suggest to use the list menu web part instead. There you can use the properties "First item CSS class:" and "Last item CSS class:".There is also the RenderedHTML property, which can be altered, so you can add any code you like into the HTML output generated by the web part.

Best regards,
Boris Pocatko