Agreed, if you use percentage values for your tables, divs, etc... your page will appear essentially the same on all screen resolutions. As for images, I'd suggest not using percentage values for those because you'll get distorted images on certain resolutions.
I agree that using percentages is the best practice. I always use a dynamic table that can expand via percentages to fill the screen.
But you can use pixels for specific items that you don't want to allow the size to change. For example, if you have a navigation bar on the left, that can stay a static pixel value. Or if you have a box that contains content that has images that use use to border it - it must stay fixed in some parts, say like the corners, while the width and height of it can expand dynamically if you want.