I'm extremely new to Media Queries so I was playing with the min-width: attributes with my Firefox 12.0 and noticed that it just wasn't working. After some playing around and after experimenting with this lovely website
http://barrow.io/lab/media-query-viewport/
I found out that the minimum min-width that my Firefox supports on my machine (it's an XP box) is 615px. Why? I'm trying to play with Media Queries so that I can make a website that works well on many devices as well as desktops. This includes devices that are 480 and 320 pixels wide. With Firefox not allowing me to test the smaller widths it's going to seriously affect my development.
Is there any kind of a work-around for this other than trying a different browser?
As of this: http://support.mozilla.org/en-US/questions/772847#answer-125895, Firefox supports no more than 480 width, so if you want to test for 320 px, you must use a different browser. I would point out that if you want to test smartphones on your site, you should be using smartphone browsers on smartphone hardware... not just desktop browsers set to really small resolutions, which is what it sounds like you were trying to do.