too hot

My recent nemesis, the oven, made me feel like a baking loser. See lemon cakes #1 and #2 for a memory refresher. A couple of weeks ago, I bought an oven thermometer and when I made a pizza last week (artichoke hearts, mushrooms, feta and garlic on a whole wheat crust), it indicated excessive heat in the oven. I had set the oven for 400 degrees, expecting the oven to be about 50 degrees too high. When I checked it, the thermometer said 500! I turned it down to about 325, but when I pulled the pizza out (early), I think the thermometer still said 500. I haven't baked since, but think I will have to investigate this oven issue before I do. Maybe after I do the work I am avoiding.