This tools allows you to check the total download size of your page(s).
This check is as comprehensive as we could make it and checks for css, images, pages, inline frame pages, frame pages etc. and recursively checks any parseable files found, a complete list with the links is presented on completion.
It can detect page compression and will show you compressed and uncompressed file sizes (real, not estimated). Due to the extensive checking you need to have a little patience with large pages.
This tool is far from perfect and is meant to give a quick indication of the page size only, for a more in-depth and accurate analysis you need to use tools like Firebug with Yslow or similar.