You have the following in your site template css (
http://awubasdn.websites.xs4all.nl/modx/_css/3col.css):
a:hover {
color:#fff;
background:#369;
text-decoration:none;
}
That bolded makes all links have that blue background color.
"He can have a lollipop any time he wants to. That's what it means to be a programmer."
The slimbox "dialog" is not truly modal, it is written on the page via javascript, no new windows are created for it so all styling / js etc on the page will affect to it too. That’s why you have to be careful to not collide with the slimbox js / css.
"He can have a lollipop any time he wants to. That's what it means to be a programmer."