The way that myOpenID does user feedback on pages with forms is understated and functional. In their HTML source, they give this content the “alert box” class, and have a link to dismiss the message at the upper right. This seems very Facebook-esque, which leads me to believe it's a widely seen/used/understood user interface element. Not too long ago, I coded a site that had UI messages very similar to this, with a jQuery timer that hid the message after a few seconds. I'd bet that no matter how many seconds it waited to remove the message, it was wrong. It also slid content up the page without a user input — another no-no.
I should note that the green trim around the main content area is clipped weirdly because of my screenshot dimensions, not due to their design. It looks much better with the rest of the site chrome.