I run into little issues like that from time to time. I mainly use this technique to fix IE8. Here's my fix:
First I install: https://github.com/rafaelp/css_browser_selector
This gives me browser and rendering classes for each browser:
<html class="gecko firefox firefox26 mac">
Then in my SCSS, I can do this:
.foo{
display: block;
.firefox & {
display; none;
}
}
This example hides .foo in Firefox. Using a & after the selector looks back up the tree. Isn't SASS awesome?!?!?
Alternatively, install the script and create a separate firefox.scss and just start it like so:
.firefox {
// Do stuff here
}
As a rule, feature-detection using something like Modernizr is easier than playing to specific browsers, but sometimes you need to address various browser issues.