Linking a custom call to action button – Responsive Theme

Hi. This is regarding, changing the appearance of the call to action button using the Responsive Theme. I’ve made a custom call to action button using the below css. However, with this change I’ve lost the ability to link the button to a page. Does anyone know how to do this? Also, I have a child site, so I shouldn’t be able to mess things up too badly! Thanks in advance for your help.

.call-to-action {
background-image: url(http://…png);
background-repeat: no-repeat;
background-position: center;
height: 100px;
}

a.blue {
display: none;
}

a.button {
display: none;
}