Misalignment issues

My theme here has a header image spanning across two columns. In Firefox the header image is a couple of pixels wider than the two columns and in IE it is a couple pixels narrower. If I change the header image width to line up correctly in one browser the alignment difference is very noticeable in the other.

#intro_right {

width: 898px;
padding: 0;
background: url(images/intro.jpg) #bcceda no-repeat;
color: #547592;
margin: 0 0 6px 0;
height: 199px;
border: 1px solid #545454;
cursor: pointer;
}

The 898px above is what I have been changing but I figure that there is a better solution.