In my experience, this is usually because you typed it in wrong, or your browser is supposed to store it, and lost it, or you're trying to access a Silver member area when you're a Standard member.
Here's a way to get a reminder of your password.
If that doesn't work, email me, making sure you identify yourself (you'd be surprised how many people don't, and assume I can work it out from their email address, which I can, but not if this is the first time you emailed me from there) and explain the problem.
There's also the possibility that you're being censored. Here's what you can do to find out, and change it.
With Microsoft Internet Explorer, sometimes it doesn't even give you a chance to type in your password. In that case, you can try this
If none of the above work, then email me at 
.
Make sure that you tell me who you are, so I can look up your details. If you give me the last eight digits of the credit card you joined up with, or the email address you gave when you joined, or the name and address that you gave, that would help me.