Mouse over "Profile" and when the drop-down menu opens click on "Account Settings".
Mouse over "Modify Profile" and when the drop-down menu opens click on "Notifications".
Once the "Notifications" window opens uncheck the first box beside "Turn notification on when you post or reply to a topic."
Once the box is unchecked click on "Save settings" located on the lower right hand corner of that section.
Maybe I got it right.
Ed
ETA: Just in case someone is wondering...