Someone notified me of a problem they were having testing a responsive site using Firefox. The site wasn’t shrinking in the browser window. The media queries were in place, but nothing but the horizontal bar kept coming up. However, my Firefox (16) worked fine along with my other browsers. I did some digging around and found the reason behind this issue.
Basically, depending on what add-ons/extensions you have installed to make Firefox better, these may prevent you from testing your responsive site. The solution is to disable your add-ons until you find the one that’s causing the problem. Or it could be Firefox’s menu bar: you might have to change the way it’s displayed to resolve this issue.
I can’t say this is a bug in Firefox because desktop browsers were never designed to shrink that small. In the real world, only web developers do this for testing. So, if you’re going to test responsive sites in Firefox, disable your add-ons, modify your menu, or use Chrome and IE9+ instead. Apart from my Android device, I also use two other tools below for responsive testing:
A bookmarklet by Victor Coulon – This will allow you to view your site in four general mobile sizes: iPad and iPhone (with both portrait and landscape). Screenqueri.es – This will allow you to resize your site without resizing the browser window. This is much more effective for me because I set break points based off layout and not device widths.