I know this concept / script Justin Luster kindly provided works in v9 ...
1) Create a Free Format question named "screen".
2) Create a variable named "width" and make sure it is of type "hidden" and also set to "whole number".
3) Enter this HTML for the question:
<input name="screen_width" id="screen_width" type="hidden" value="">
<script>
$(document).ready(function()
{
$("#screen_width").val($(window).width());
});
</script>
I was testing in v7 and when testing, the free format variable is blank.
Do you have a solution to have it working in v7?