I'm very grateful to you. Thanks a lot.
At last I could find a working mod. I've tried most of the other mods which is intented to auto resize oversized images. They may work for some others. And thanks to them as well.
But this mod worked both on IE and Firefox 1.5.0.4 on a vB 3.5.4 forum.
BTW I've customised resizevbimg.js for 680px and translated the phrase into Turkish. No problem with doing that
Thansk again. I had been really bored with big images in posts and signatures which spoil the view.