ASP.NET Gotchas

Some gotchas that have caused me to waste so many hours on so many projects:

1) Many CSS features, such as "margin: 0 auto;" will not work unless you have the correct !DOCTYPE:

!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"


2) When migrating from VS2003 to VS2005, the migration tool will add this piece of evil into your web.config:

xhtmlConformance mode="Legacy"

This will prevent AJAX from working. Ridiculous!

See here for Scott's explanation:
http://weblogs.asp.net/scottgu/archive/2006/12/10/gotcha-don-t-use-xhtmlconformance-mode-legacy-with-asp-net-ajax.aspx

3) HTTPModules can cause all client side validation scripts to stop working. I don't have any answer on how to fix the problem...sorry. But if you requiredfieldvalidators don't work - it's something to check.

4) runat=server :)