Mac users and Internet Explorer
IMPORTANT INFORMATION

Mac users and Internet Explorer

If your are using a Mac operating system and Internet Explorer as your browser, you will experience difficulties using the secure payment page on this site as well as any other secure sites you may visit. You are strongly advised to install a second browser to overcome this problem with Macs.

Here is something I found on a forum. Its a comment from Paypal regarding Mac's Internet Explorer -

"If you are encountering difficulties using Internet Explorer on Mac
OS 9.x and below, we ask that you consider using a different browser at
this time. The error you are encountering is a well-known and
documented issue with Internet Explorer's inability to recognize valid
security certificates.  Approximately one year ago, Microsoft
announced the end of development for future versions of the Internet
Explorer browser for the Mac. With this in mind, you will want to
begin looking at various alternatives available for your Internet
browsing needs."

Alternative browsers are Firefox, Safari or Opera