Couple of Mac questions.

Hi all. Ok here are the two questions one of which is driving me crazy. If i'm in Yourufukuru and I get a mention or message, the notification center pops up.I close it and the menu bar stays up. I have to command tab around to get rid of it. How can I stop this behavior? I've checked, and the twitter share button is in the notification center, which I want, so I can share websites and things, but i really don't want ot to keep saying, mention by, message from... Oh the dialog is mention by, the name, then close button or sow button. Here's the second question. How do you mention, someone on facebook? Not tag them, but mention them? You used to be able to write, @ Siobhan and it would find the person you were looking for. I don't know how todo it and i'd liek to if possible. I knowhow to tag someone with the button, so I'd like to learn this too. I'm also using the main site, not the mobile site. Thanks for any help. by the way, night owl is not in the notification center, just the twitter share button, as well as the twitter app and it says allerts. Thanks for reading this far sorry it got jumbled.