show/hide div based on browser size using ONLY css?

Question

I am a trying to get some divs to show/hide based on browser size, using only css media queries... but nothing seems to be working... please help if you can and let me know

Answer 1

class name can't be a number, and cannot start with a number in CSS. Here is an example where I changed the class name and it's working good

http://jsfiddle.net/RtTsy/

Answer 2

class name can't start with the digit. change it to e.g. x700,x490,x290 and it should work