I always used the Opera browser on my Milestone and Milestone 2 phone.
On PUCRS, the standard and the Firefox browser simply can't pass the login check to access their wi-fi... =/
obs.: After that I and a friend developed a java program to login without any browser, it's faster and doesn't affect all the tabs you have in your browser.
The result was the college didn't accept our program (developed to android, and PCs -Java) because they are so proud and they do not like to thanks their students for help...
By the way, the program is PUCRS Portal Login