CSS HELP: 2 column div stacked on mobile device

For some reason I’m having a hard time with this so I hope someone can help me here.

On my website I have 2 column div displaying location info for a client. What I need it to do when it shows up in a mobile device I want those two columns to stack rather than side by side. I tried using min-widths to get it done with no luck.

Anyone have a general example they can show me?

Just use media queries. When mobile, just unfloat the columns (and by default, have them float:left’d)

http://www.w3.org/TR/css3-mediaqueries/