Every now and then a website becomes super-slow (but not broken) because there are too many people looking at it at the same time. When I try and view such a site, say with Firefox, I can see that it is downloading all sorts of components of the site because of the progress information printed at the bottom of the window and I'm sitting there thinking "If only the browser would show me what it's got so far. I don't care if its a jumbled mess, I just want to see what you've got". Does any browser offer such an option?
You can use the "Net" tab with the FireBug extension for Firefox.
You can even extend the Firebug extension with Yahoo!'s YSlow addon for Firebug.