Trying to get my one of my divs when clicked to call a function but it doesn't seem to be working???

I just noticed that only one solid pixel in the div border which i will eventually set to 0px calls the function but I want it so the whole div area calls it??

<div id="headersignup" onclick="signup();"></div>
#headersignup{
 position: absolute;
 top:0px;
 right: 30px;
 display:block;
 width: 60px;
 height: 30px;
 line-height: 30px;
 display: inline;
 vertical-align:middle;
 background: url(../pix/signup.png) no-repeat center;
 border: 1px solid #ff0000;
 margin: 0px 0px 0px 0px;
 padding: 0px 0px 0px 0px;
}