How are your site displayed in a mobil phone? You can find that out here: http://www.google.com/gwt/n

Google takes HTML pages normally viewed on a computer and translates them so that you can see them when you're on the go. During this translation process, Google analyzes the original HTML code using sophisticated algorithms. In order to ensure that the highest quality and most useful web page is displayed on your mobile phone or device, Google may alter images, text formatting and/or certain aspects of web page functionality.

Try this for example and see how it looks like.

It’s pretty handy, instead of install another .css in your server, you just can give the gwt url to anyone who wants to look at your page through a mobil phone.