Is there any software (freeware) which will automate tasks on my system, so it can be used to log in or log off any site at specific time?
I had a software called Robotask but couldn't understand how it works.
Yeah, you can definitely use Windows PowerShell for this purpose. Granted, you'll have to get used to writing some code, but you can automate Internet Explorer via the IE COM API. Here's a short example to get you started:
To do the above, it would be:
Hope this Helps