Normally when you have a div created in html. You can check its width with offsetWidth or style.width (if declared). However if the innerHTML is changed such that the width of the div is also change, neither of those functions work (not sure, but they haven't in my cases).
some code:
var div = document.createElement("div");
div.innerHtml = "asdfasdfasdfasdfsdfasdfasdfad";
alert(div.style.width); // this is nothing
alert(div.offsetWidth); // this is 0
How do you get the width of the div above?