absolutely positioned element in a button problem

have a wierd issue. for the life of me can't trace this back (its gonna be a noob prob I am sure - just can't see it!)

I have a relatively positioned and a span within that is absolutely position right:0 top: 0 bottom: 0 and has a width of 20px....

fine in chrome/safari ie9 (not checked 7/8 yet) but firefox is setting right: -6px botom -3px...

Pretty stumped - i've been looking for a while and the trees are getting in the way of the woods...

here's the page - and its the button on the search form in left hand panel.

demo page

开发者_开发问答Any help much appreciated.

---

I gave a quick play with firebug on it, and found that

.panel button {height: 1.5em} (public-layout.css, line 102)

and button {font-size: 0.9em} (public-tipography.css, line 60)

Change the layout in some way.

---

button span {
bottom:0;
height:20px;
position:absolute;
right:0;
width:20px;
}