public wifi, connected but no internet access

How do i get my browser to go to the signup/login page when accessing a public wifi network. I always have to fumble around and try to guess what page to type in, then i can enter the code or accept the user agreement to gain access.
Usually the browser just tries to go to my startup page, which wont work. Or a little popup ballon appears saying i need to enter additional information, but when i click on it the browser always tries to open my startup page. Please tell me there is an easier way!

I think if i change the default page to google or something the signup page will automatically popup. Does anyone know if thats true?