Supported Browsers

Hi Mikrotik guru’s..
I have a client using a Mikrotik hotspot system with (I have been told) the latest versions running on it. The problem I have is that some users are experiencing problems when purchasing extra download allowance via the paypal feature. Sometimes it works, other times you get timeouts etc.

I firstly want to know if there are certain browsers that this does not work well with?
Are there java issues that I should be aware of?

Any pointers would be appreciated..

Cheers,
Chris