You can also specify both width and height (example: width="250" height="500") and then you will whack up the aspect ratio.
I've had to do that a couple of times when an original image's aspect ratio was off and my OCD couldn't cope with that.
“Only if you specify one parameter”
Thanks. I always thought you had to specify both. I use Microsoft Free Expression for most/75% of the HTML and photos I post here