Tool to Find Out What The Browser is Downloading

My PHP Apache website starts to load a part of the content, then it seems to stop loading and then it appends the rest of th开发者_如何学Goe page.

I would like to know if there is any tool to find out what exactly is being load at the moment by my browser.

I prefer Firefox, but any browser works.

Following the advice of @Ehtesham, I am using Firebug for this purpose. I didn't know that it had this functionality.

To download firebug for Firefox: Download Page