For some reason, in some clients my DIVs are stacking when they should be side by side. Here is a Litmus, and take a look at Outlook 2000 for example:

In other Outlooks it is not even in two columns like intended.

Here is the code used to create this in JSFiddle:

I am new to all this so any advice you can give me on my proof of concept so far would be greatly appreciated.