yes u can do that thro web.. that helps us..
http://msdn.microsoft.com/wn3/locales/help/help_en-us.htm#RateAPost
see this snippet i took from msdn help..
isnt it possible in usenet
Rate a post as an answer (or not an answer) to your question
(Note that you cannot rate a post that you have authored.)
When someone replies to a question you asked, you can rate this post as an
answer, or not an answer to your question. By rating a post as an answer, you
help others find the answer more quickly, you give credit to the person who
posted the answer, and you help increase the quality of answers in the
discussion group.
In the thread pane, select the post that is a response to a question you
asked.
In the message pane, do one of the following:
If the post answers your question, click Yes next to Did this post answer
the question?
If the message was not helpful to you, click No next to Did this post answer
the question?
The post you rated is now marked as an answer, and the thread is now marked
as an answered question, and will be returned in search results.
Additionally, the person who posted this answer is credited with an answered
question (this is added to their profile information).