The links they use are normal textlinks with underlying pictures.
There are two places where images are used as text.
"Home" and "Ajuda" are just GIFs.
"Loja" and "Profissionain" are different. The code for "Loja" is:
<img src="ttf.php?text=LOJA&size=6&font=STAN0765.TTF&bg=641D09&fc=FEFEFE" border="0">
In other words, the image is being generated on the fly.
Neither is an acceptable implementation, because no alt text is provided, and the links are inaccessible to users who are blind or aren't using graphical browsers.