You accidentally typed Ctrl-Shift-E, thus turning on Track Changes. If
you're in Word2003, then a Track Changes toolbar has appeared, and on
it you'll find a button with a red X. Alongside it is a tiny triangle
-- click on that, and from the dropdown, choose Accept All Changes.
Also on that toolbar is a button that turns Track Changes on and off
(it's hard to describe, but it's bright when it's on). Or you can type
the key combination again, or you can click the TRK down in your
status bar at the bottom of the window. (Black = on, gray = off.)
In Word2007, the same controls are on the Review tab of the Ribbon
(and the other two ways of turning it on and off stll work).