valid HTML 4.01 picture -> missing transparency

hi guys, i think there is something wrong with this "Valid HTML 4.01" Picture. there is a little, white stripe at the right of this picture, but normally it should be transparent, shouldn´t it?

ok, my english is not very good, the best would be yo take a look at my site, and you´ll see what i mean:

http://www.kaffeecontrol.de

these two pictures in the bottom left corner; one of them (the "Valid HTML 4.01" Picture) has this white stripe, and it don´t looks like the other one...

it would be nice if the W3C-Team could correct this.

THX