How can I make my divs stay the same size depite adding content?

So I imagine this is a pretty trivial question for most, but I am working with a grid like class of divs, and whenever I dynamically add content to one div, the whole row of remaining 开发者_StackOverflowempty divs shifts down.

There may be something that I am just not understanding about divs, but after doing some research on the web, one post said there was something that JavaScript could do to help, but that he wasn't going to talk about it. Does anybody have any ideas? Thanks in advance!

div
{
  overflow:hidden;
}

You may want to look at the overflow CSS property: http://reference.sitepoint.com/css/overflow