Simplo Theme- Header Image Problem

Hi All,

I just installed the Simplo theme for my blog:

http://www.site5.com/wordpress-themes/

I am having issues with the header image. I want to use a larger image. I tried to look up how to change this and found that I am supposed to change this:

#header {
position:relative;
background:url(images/bk_dotted_horiz.png) 0 100% repeat-x;
height:100px;
margin-top:10px;
margin-bottom:13px;

I have read that I should just need to change the height size. however, I’ve tried changing it and nothing happens. No matter what I change the height to, the area does not increase and my image ends up overlapping with the main menu bar. I don’t understand what I am doing wrong. Do I need to change something somewhere else? I even tried playing with some of the other numbers in the style sheet like the margins and those don’t change either so I know I am doing something wrong. Why won’t any of my changes show up?