http://blogs.msdn.com/mikhailarkhipov/archive/2006/12/25/repairing-visual-web-developer-intellisense-issues.aspxI'd like to summarize a few known issues with VS/VWD intellisense and respective solutions or workarounds. Symptom : No markup validation and no code intellisense. When you type invalid element or attribute, red squiggly line does not appear. No C#/VBen-USCommunityServer 2.1 SP1 (Build: 61025.2)