Max key length error

[Brian Rivet]

Hi 
 
I'm new to MySql and I'm trying to set up a database table, and I keep
getting an error saying:
 
Max key length is 500
 
I have looked everywhere I can think of but I can't find an explanation
for what is causing the problem so I can fix it, can anyone help me?
 
Thanks,
 
Brian Rivet