add1 = '<a href="http://www.halfadot.com" target="_blank"><img src="../images/card-1.gif" border=0></a>'
+ '</a>';

add2 = '<a href="http://www.halfadot.com" target="_blank"><img src="../images/card-2.gif" border=0></a>'
+ '</a>';

add3 = '<a href="http://www.digitalmidget.com" target="_blank"><img src="../images/card-3.gif" border=0></a>'
+ '</a>';

add4 = '<a href="http://www.digitalmidget.com" target="_blank"><img src="../images/card-4.gif" border=0></a>'
+ '</a>';

//The number below, must be the same as the number of banners you have.
addnum = Math.floor(Math.random() * 4) + 1;

document.write(eval("add" + addnum));