Thanks for your input...
Sorry if I haven't explained myself very well!
Please see attached images.
Basically what I want is to present my content in divs as follows:
If someone has a wider screen, then I would like the divs to line up in two colums as in image 1.
If they have a smaller screen then I would like it to line up in a single column as in image 2.
Hope that makes sense.
If I can't do this this way (which would be really neat and simple!) then I think the alternative is to start with two container divs and change the widths of them and move the contents around to get the same effect but it would be much messier I think.