What happened ?

I was bragging on myself for learning how to put pictures on my posts, signature etc. etc. and then.... out of nowhere the pic in my signature went supersize on me. First two days it was fine. Appeared as thumbnail size then (see below) it went crazy big. The pic is saved on photobucket as thumbnail size. Any suggestions? If I cant figure it out in a day or so I am going to take it off so I don't fill all your pages up with a life size photo of my bike.