One thing that has always impressed me is the ability of web designers to deal with browser idiosyncrasies.
For instance, knowing why this happens in firefox-17.0.1-1.fc17.x86_64 -
Needless to say, the web is littered with questions about why btn-primary background color is not always white. Most have answers, some with varying degrees of complex css. Others involve changing versions of software. All the while it might just be the URL used to view the page.
Test in a production environment.