Give your <div>'s an id like this:
HTML Code:
<div id="cart"><a>Go shopping</a></div>
<div id="advertisement"><a>Win something now!</a></div>
Then, you can use css to style it like this
Code:
#cart a{
color:#00ff00; /* Green Link Text */
}
#advertisement a{
font-size:10em; /* Ridiculously huge link text */
}
You can give any element you want an id to uniquely identify it. There's plenty of information available here and on google if you need more help. You might want to research css classes as well; they have a pretty similar purpose but are for a slightly different situation.