Differences between Firefox and Chrome in the Omega theme
As I previously mentioned in comment, its not related to Omega nor Drupal, but you can still try to use normalize.css.

A modern, HTML5-ready alternative to CSS resets (as used by Twitter
Bootstrap, HTML5 Boilerplate, TweetDeck, Soundcloud, and many others)

Alrternatively as you didn't provide any link or capture, I suggest to check your styles and libraries list in your omega subtheme settings, go to Appearance &gt; THEMENAME &gt; Settings , under Toggle styles and Toggle Libraries