thanks to all for the answer!

my problem with http://mec.tuwien.ac.at/ is the following:

one pc in our work ( IE 6.0.2800.1106, W2K with all patches) does not show the logos (all firewalls off). but two other shows it ... (and all other browsers: no problem)

the tag is:

div style="background-image:url(background2.gif); " ...

which made the problem in one pc ... but I think it is the problem of the one pc only ...