Thank you for taking the time to respond. As I understand it, I have a wrapper ("topheader") which is 960px wide and then 3 columns within that which each amount to less than that width. But when I try and add something below that in the code, it moves my end column on to the next row.
#topheader {
width:960px;
margin:0 auto;
}
#col-1 {
float:left;
width: 483px;
margin-right:30px;
}
#col-2 {
float:left;
width: 210px;
margin-right:30px;
}
#col-3 {
float:left;
width: 170px;
margin-right:0;
}
Clive