Paypal have said that lots of users are still using internet explorer 4 and they have even found a few users still using inter net explorer 3 that was released over 10 years ago to carry out transaction over the internet.
The problem with using these browsers are they no longer have security updates and viruses are easily passed around when using these browsers on website.
There is more information on this on bbc news.
http://news.bbc.co.uk/1/hi/technology/7354539.stm