Well, I would think Jim Rob knows what he is talking about. I specifically asked him and he said height and width are good. I think mostly for those who have dial up. It makes it load up a lot faster.
You can find the height and width when you look at the properties. There are two numbers there next to Dimensions. The width is the first number and the height is the second number.
It will not affect the speed but it will affect the size.
If you put in both height and width, as you say Jim recommends, then this allows your web browser to paint the screen faster, before the image is entirely downloaded, because at least it knows how much screen space to reserve for the image. But I'm pretty sure that you will end up still downloading the entire image, in its original full blown size.
So, depending on which web browser they are using, and how long (big images over slow lines take longer) it will take for the image to download, the user could see a more useable experience, by having the -rest- of the page displayed reasonably, before the image is downloaded.
Here are some web pages discussing this in more detail:
In short, the height and width attributes can help improve rendering speed (how quickly the rest of the page paints on the screen) but it does not enable downloading images faster.
However ... for responding to posts asking how to post images on FreeRepublic.com, I tend to think it is more important to Keep It Simple Stupid, and intentionally describe the simplest way to post images that will usually work.