Recently helped one of my friend experiencing issue while publishing website ( to a shared hosting server. Website had few managed Http Handlers to create Image Thumbnails / add watermark on images etc, worked perfectly in local IIS but never worked on published website.

By default, when you add a managed handler, the handler will run only in application pools configured to use Integrated mode. Published website was running under Application Pool in Classic Mode (which pertains to IIS 6.0), so handlers were never registered with IIS and hence never run.

So if you guys run into same situation, make sure to check that hosted website is running under correct Application Pool (Integrated Mode in our case).

Hope it helps…