I logged in with user name and password, but when I click any other link, it ask me to login again. Why is it happening?

Some computers are set to cache pages. This is done by internet cafes to save bandwidth.  Some times, your Internet Service Provider (ISP) will also use a cache server to cache pages downloaded by their users to save bandwidth and to thus cut their cost.

It seems your ISP is caching the login page when you  land at that page first.  After you login, and when u click on any other link, its just retrieving the login page from cache which it should not. It should receive the modified page from our servers, but as I mentioned above, your browser is not sending it out to our servers due to changes in default setting o0f your browser, or changes by ISP to reduce their bandwidth.

So the options for you is to Refresh the page by clicking CTRL Key and then Press F5 Key.  You should also make the setting of your browser to default,  such that cookies are allowed.  

If none of this works, or you do not know how to address the above issues yourself, you shall seek help from your administrator.  An alternate method may be to use another computer if you have access to, or change your ISP or internet cafe.

The following should also be considered while logging in:

AOL users should use Internet Explorer or Netscape to login instead of the AOL browser to avoid AOL's proxy servers.

Your login is attached to your IP address. If you are using IP blocking software, close it and try again.

By logging in, you will get a temporary cookie which will remember your Username while your browser is open. If your system is set not to accept cookies, then you will have loggin problems.

If there is no activity for 60 minutes or you logout, the cookie will expire and you will need to log in again.