ASP.NET has this thing where pressing Enter on a page will cause it to be submitted, but no submit action is taken, mostly because you can have multiple buttons on a page, and it isn’t sure which button it should consider clicked when you press enter.
The solution to this was the “__EVENTTYPE” field. Click here for more info on __EVENTTYPE.
Thankfully ASP.NET 2.0 has introduced some new features to help remove this complexity.
Scott Gu blogs about the new form defaultButton property, as well as the new SetFocusOnError property of the validators here: