Question: I have an asp page that contains a lot of data, images and objects -- and I want to know the size and the weight of those images and objects. 

Is there any tool that can give me these kinds of details?

Answer: 
You can use [YSlow](http://developer.yahoo.com/yslow/) in Firefox (and maybe other browsers); it will give you the info you need, separated by type. It also gives lots of information regarding cache usage and good practices
You might also try [Fiddler](http://www.fiddler2.com/fiddler2/). It tell you the size (in bytes) of each script, image, css, html, etc loaded during a particular page load.