Not sure what it's called - but it's the yellow pop-up window that contains the nearest post/message that appears where ever my mouse pointer is "laying"..

thanks:D

Download Mozilla Firefox 2.0
type "about:config" in the address bar and hit enter
type "browser.chrome.toolbar_tips" in the Filter field
double-click on the Preference Name "browser.chrome.toolbar_tips" to change the value to "false"
close Firefox and reopen it, yellow pop-up thingies should be gone.