How to add custom HTML Tags to Visual Studio and Avoid Squiggly Lines

Question

I\'m using Visual Studio 2013 to create raw HTML pages (i.e. index.html).

In my HTML I am implementing custom HTML tags. As such, Visual Studio underlines my custom

Answer 1

Visual Studio 2013 Update 4 removes the validation in .html files, but not in .aspx files.

Support for custom elements, polymer-elements and attributes

We no longer validate unknown attributers for custom elements as there will be many custom made tags in different frameworks. So there will no longer be squiggles under the unknown elements.

— Announcing new Web Features in Visual Studio 2013 Update 4 RC

Download Visual Studio 2013 Update 4.

Validation is only removed in the HTML editor, not the HTML (Web Forms) editor. This means that, by default, .html files will not have custom element validation, but .aspx pages will. If, like me, you don't think this makes sense, show your support by voting for custom elements in .aspx files.