A 'Web Page Profiler' is a tool that is used to measure and analyze web page performance. It is usually implemented as a browser plugin or add-on, and lets you see performance of web pages/objects as they are transferred/loaded/executed/rendered.
For Firefox, choosing a profiler is a no-brainer. Firebug is an excellent developer tool that includes profiling capabilities.
Add me on Twitter! Come follow my daily antics, links, tips and more @rajneeshgarg on Twitter!