Interdev is Microsoft's answer to web coding.  It helps you to make a
collection of pages into an application and do some advanced
coding/debugging.  Dreamweaver helps you make the actual pages.  It's way
better at writing the HTML.  In my opinion, if you can get your hands on
both apps do it.  I use Dreamweaver to do the HTML when notepad fails me and
I use InterDev to help me with the ASP workings.  Hope this helps,

 - Danger