You might have seen private forums which doesn’t allow users to read contents without registration . Here is method by which you can browse and read  forum topics without registration.

This method actually uses a Firefox addon user agent switcher which can switch and assume different user agent profiles from Firefox itself .

Usually some forums blocks guests from accessing forum contents , but they allows search engine bots like Google. So here we pretend ourselves as search engine bots , using user agent switch Firefox addon .

Download User agent Firefox addon .And after installation,select to create another user agent from the options menu of the addon . Add following as description .

crawl-66-249-66-1.googlebot.com

In the users agent field, add the following

Googlebot/2.1 (+http://www.googlebot.com/bot.html)

Now Start browsing with the new user agent .

Download user agent Firefox addon and browse forums without registration .