Jaky je rozdil mezi ASP.NET Web Application a ASP.NET Web Site ve Visual Studiu 2005?

Kdyz si udelam ve VS2005 ASP.NET Web Application, tak to vyzaduje kompilaci do DLL, jinak browser hlasi chybu.
V pripade ASP.NET Web Site si to kompiluje IIS automaticky.
Ale zase mi VS2005 pod Windows Vista pri otevreni solution rve, ze
The site 'http://localhost/xxx' is currently configured for us with ASP.NET 1.1.4322.2407. Microsoft Visual Studio has been designed for use with ASP.NET 2.0; if not configured some features may make incorrect assumptions, and pages designed with the tool may not render correctly.

Would you like the site to be configured for use with ASP.NET 2.0?
IIS ma standardne nastaveno FW 2.0 a zmineny web take.
Pri browseni jede web tak, jak ma.