Actually anyone can Verify any post...
Intentionally, Verify should be done by OP (Original poster, who ASKED the question, and got an answer that solved his issue), but now and then it's done by somebody else, mainly in cases when the answer is obviously correct or only possible solution.
A couple of times I've "Verified" my own answer - Q was straightforward & simple and had one-and-only solution which I wrote. Occasionally I verify other poster's answers, too, if I see the Q answered correctly --the OP then sees it's the correct solution, not a maybe-suggestion only-- but mainly in those forums only which I moderate, it's quicker, than adding a post like "I agree, that one is correct".Sometimes I only "Suggest" some answers, letting the OP himself to decide got he a solution or not, depending on the details he might haven't disclosed.
Such type of Verifying/Suggesting instead of OP is mostly done either by moderators or by members, who are actively following the forum and regularly post answers themselves, but again - anyone who finds an answer to be unambigously correct can Verify it.
added: Besides, this helps to those forum users, who search / list through the forum for their problem - if they find a similar Q to their own problem, they can see if it's answered or there was a long "discussion" which actually didn't solve the issue.
Wow that's really a nice reply.
Thanks dude :)
Just a little correction. Verification can only be done by either the OP (original poster) or one of the moderators. As Modris say, then sometimes the answer is so straight forward, that it's ok for the moderators to verify an answer.
But all members are able to suggest an answer as the solution, both their own answers and answers posted by other members.
Sorry, Manish, I misleaded you - being myself in moderator's shoes, I didn't know that enabled "Verify" button for all posts is one of moderator's additional privileges in the forum.
But I'll use these privileges right now to verify Erik's answer, which "is unambigously correct"
updated: Wow - turned out that even a moderator can't "Verify" everywhere, only in forums he moderates - so it's up to you to to do it here (or Erik and David, who are Admins of DUG)