Nothing wrong with your Safari. Their website forwards me to a blank page
http://www.oldnavy.com/browse/info.do?cid=8759
http://www.bananarepublic.com/browse/info.do?cid=8808
http://www.gap.com/browse/info.do?cid=8768
Which if you open it on Firefox says that Firefox 1.0 and Nescape 7.0 for the Mac are the browsers that are compatible when I go to the page that Banana Republic, Oldnavy, and Gap forward me to. Going back to their homepage on Firefox appears to work. This is clearly a case of their not following http://www.w3.org/ and accessibility standards. I suggest contacting their webmaster, and use http://www.anybrowser.org/ 's form letters to ask that they use more open standards for their website.
Firefox can be downloaded here:
http://www.mozilla.org/