IE8 has a known bug (per connect.microsoft.com) where typing or pasting text into a TEXTAREA element will cause the textarea to scroll by itself. This is hugely annoying and sh
I think the best way to describe this bug is that if you set a width for the textarea using CSS, and this width is too different from what the COLS field would render, IE8 shows the weird problem, with the skipping scroll bar.
So, if you have cols="10" and textarea { width: 600px; }, the problem will show up because IE8 will use the width calculated by the COLS attribute for the scrolling, instead of the CSS one that's overriding the dimensions.