There is a “report” button on the right side of your post. It can be used to flag spam.

If you will use search you will find couple of related discussions. In short answer is “no”.
Use report link as dialingo suggested

no there is no option for downvote, use report as dialingo said

Well well, 3 people telling me the same thing.
I was just reminded of this old indian ad : http://www.youtube.com/watch?v=DkKbLLcJG4I

It is OK that the “worst post” with zero rating, and the best practice with big number of rating. might no need to breed “hatred” using downrate :)

I am always confused between options “link” and “report” options. Can somebody clarify what do they mean??

There is no tool-tip for them, and I don’t get any feedback after I press them. How do I know what happened after I pressed them?

If you click on “link” then you get a web adress like this:
http://developer.qt.nokia.com/forums/viewthread/7709/#45281
Which you can use to point to a specific post.

Report is for reporting spam or everything that is not acceptable following the forum rules.

But word “report” does not convey that message. Why can not it be “spam”?? or “report spam”?? which makes it very clear about its meaning.

“Report content” is the title of the dialog that appears and has a more general meaning than just spam. I only used spam as an example.

You can also use the report button to, for instance, report to the admins that a topic is getting out of hand, or that you think somebody is making a personal attack on another user.