I came across a little snippet of CSS code that adds an icon next to URLs based on the type of data they are linking to.  This code works perfectly everywhere except in a skin.css file.  Any ideas why?

a[href

Do you have an 'icons' subfolder under the skin folder with the 'icon_mailto.gif' file in it?

You could also try this (it should give you a pencil on paper gif):

a[href^='mailto:'] {
 padding: 5px 20px 5px 0;
 background: transparent url(../../../../images/action_settings.gif) no-repeat center right;
}