UBB.threads PHP Forum Software Community Forums Resources and Customizing How Do I? Clipped images problem

I was wondering if someone can help me with a problem I am having with images in posts getting clipped on the right.

Example: images like


are appearing as



I do not have this problem on my computer, though some users (with different DPI/font size settings, I presume) are having it on theirs. What is the best way to customize the board to work with a variety of browser settings?

For that matter, while designing HTML pages in general, should I be setting my column width based on Ems or Pixels?

Any advice is appreciated!

MW