How to align my link to the right side of the page?

Try the following:

a.buy{
  color: #2da1c1;
  font-size: small;
  text-decoration: none;
  float: right;

}
a.buy:hover
{
color: #f90;
text-decoration: underline;
}

(1) you have float: left; on the example code (2) maybe if you add float: right; to the div it will help?

Try float: right:

a.buy {
    color: #2da1c1;
    font-size: small;
    text-decoration: none;
    float: right;
}
a.buy:hover
{
    color: #f90;
    text-decoration: underline;         
}

Another way would be:

.content {
    position: relative
}
a.buy {
    color: #2da1c1;
    font-size: small;
    text-decoration: none;
    position: absolute;
    right: 0;
}
a.buy:hover
{
    color: #f90;
    text-decoration: underline;         
}