Wanna share with you what I came across on the net. This guy Omar Al Zabir really knows what he is doing! Look at that article describing ASP.NET Ajax runtime and how to reduce overall download size. He is giving an example with his www.dropthings.com
“Let’s do some ASP.NET runtime analysis on www.dropthings.com. Those who don’t know what it is, it’s an open source start page I made using ASP.NET Ajax, .NET 3.0 and Linq.
ASP.NET Ajax has a pretty big runtime which consists of Core Framework, scripts for UpdatePanel, Preview Script required for Drag & Drop. Additionally I need Ajax Control Toolkit (ACT). All these add up to a staggering 564 KB of download in 12 script references on the page. The download size mostly depends on the usage of extenders and Ajax features.“