Always visible scrolls and CSS styling

Hi!
Here I have a little trouble: when I put a grid into a tab of a tabset, then on a plain webpage, where is no themes around, everything is fine as on a showcase.

But when theme is “around” (let’s say, SmartGWT app is embedded into some webpage), then only in a Firefox (!) grid always gains vertical and horisontal scroll as well, as entire tabset gains horisontal scroll below. It scrolls only few pixels though, because inner object is just a few pixels wider.

The question is: what style property I have to look at in the theme in order to make sure this does not happens?

I tried to expect elements, disabling CSS styles, but simply got lost what might be wrong. %(

Is there any general tips how to embed SmartGWT application into any website and what to be cautious of regarding CSS, in order SmartGWT widgets still look like they should?

Thanks a lot.