This is an article by Clinton Forbes explaining why scripting languages are popular for web applications.

As far as performance goes, both the ASP and ASP.NET systems hold up well in times of high-traffic (usually around the time of major sporting events). However the performance of our systems is not due to any inherent characteristics of the ASP or ASP.NET environments, it is due to careful consideration of which parts of the applications are critical for good performance and which pieces of content absolutely must be cached to have any hope of coping with high-traffic.

Go read it (dead link)