httpmodules httphandlers, whats the ideal use of them? when to use and when not to use?

Question

I have some questions about httpmodules and httphandlers, i am a little confused of the real need of them, i created many websites, but rarely used them, sure i lost a benefit f

Answer 1

I will quote the usage, people have already given good definitions.

HTTP handlers
Imaging you want to render the sitemap of a website to search engine crawler, rather than popping up the file save dialog (The file save dialog appears when ASP.NET/IIS do not have a default handler for the file type requested, ex. txt). I wrote an HTTP Handler to construct sitemap files on the fly (pulling sitemap info from DB).