The compile is a one time event. And it depends on what kind of project you created.
if you create a asp.net web site, then pages are compiled on the fly - but ONLY the first time they are used - use by anyone. So you don't have to care or worry about this issue. But to answer your question? They are only compiled one time. Not each time.
If you create a asp.net web site application? Then when you deploy the site, all code and pages are compiled at deploy time. No runtime compile on the fly (that one time, first time) occurs. and I belive that you can deploy without a pre-compile for a web site application - and you notice quite a delay the first time the site is used as a result. But in this case - only one .dll for the site is created. This is really simular to a desktop application. You compile the project, and you get one .exe or one .dll. You may well see/find some addtional .dll's from libraries that you referenaced in the project also included in the bin folder.
As for the .dll? As noted, it depends on the type of site you created. If you created a asp.net web site application, then everything (most) is compiled into ONE .dll that resides in the bin folder. So each compiled page thus does not have a separate .dll.
The site is thus pre-compiled (or only compiled one time). For a asp.net web site (not a web site application), then you should/would in theory see a new .dll for each web page if you created a asp.net web site in place of a asp.net web site application. Some prefer a web site, since then you can update ONE page without a whole site re-compile.
But, if you have your own IIS server, then choosing a web site application is preferred. One big difference is that you can create custom logon and authentication providers with a web site app, but you can't with a web site. You can still have and create logons for that web site, but a web site application allows you to over ride and build your own authentication providers.
You as a general rule only want to create a asp.net web site application if you have your OWN IIS server. For most hosting plans (say low cost ones), then you have to use a asp.net web site - not a asp.net web site application - and in that case, then .dll's should appear for each web page in that case.
But as noted, in either case - once the page is compiled, it does not re-compile over and over each time such pages are used.
