Why doesn't my tablet connect to free wifi?

On a recent trip to New Zealand, I tried to send emails from McDonalds, Christchurch Airport and Dunedin Octogon free wifi areas, I could not connect on all occasions. I also have some problems when connecting to private wifis that require a an ID and password. Once a mistake has been made and the incorrect ID or password is entered, I find it difficult to re-establish the page that allows you to enter the ID and password. Any help would be appreciated especially as the tablet was purchased for wifi connection when travelling overseas.