If your toaster is now 10 year old I would suggest replacing all elements, retaining the working removed elements for reinstllation at a later stage. Sounds funny, here's the reason. When elements are used over a long period there ability to reflect heat decreases therefore if you just replace 1 element and leave the other old ones in the side of the slice of bread next to the new element will brown at a different rate than the side near the old element. Either have all new or all old elements in the toaster.
sunshine, October 2007