A new and very dodgy vulnerability has been found in IE that allows fraudsters to create web pages that pose as other sites; and it is increadibly simple to set up. A few weeks ago an ex-colleague asked some advice after receiving an email with a link to a spoofed version of the e-commerce section of their site, so as you can see this is could be pretty nasty. You can find out more information at Secunia.com.
Basically, be very careful using e-commerce links from emails and untrusted websites. Or else use FireFox.