How can I remove the border from link images?

I have an annoying reddish border around my next/previous link images.
How can I remove them?

Thanks in advance!

I've got the following link on a page;

The style sheet looks like this;

A:link
{
COLOR: mediumblue;
TEXT-DECORATION: none
}
A:visited
{
COLOR: darkblue;
TEXT-DECORATION: none
}
A:active
{
COLOR: royalblue;
TEXT-DECORATION: underline
}