This is a function of a bad cookie or preference file. First, delete the Cookies in your browser or reset Safari from the Safari Menu. Decondly, clear the browser cache. Then mosey over to Users/Your User name/Library/ and throw out com.apple.Safari.plist.
Another neat trick is to fool most any web site. Download
Safari Enhancer and enable the Debug Menu. Then in Safari choose the menu item "Windows MISE 6.0" when you are on the top page of the site you want to access. This will help fool the stupid HTML programming of that web site.
Personally I am making it a habit not to patron a web site that only caters to one segment of the potential surfing customer. That company does not deserve my money if they constantly have bad customer policy by discriminating against me because I don't follow the herd in computer choice. If enough people do something like that then maybe that company will change it's way. Besides, send the offending web site a kind word about you will no longer shop there because you do not feel safe using a bug ridden unsecured defective web browser. I say this because this problem does not only affect Safari. It affects ANY non -IE browser on any platform. It is just a sign of bad web html programming.