Can I stop ReSharper objecting to Ionic HTML tags?

Well I'm a big believer in writing valid html. Standards are there for a reason, and we can't complain about Microsoft not following them with IE if we don't follow them ourselves.

I did some searching and couldn't find any information on whether Ionic could be written as valid html.

So personally were I in your position I'd either consider whether writing an XHTML DTD that supported Ionic's mark-up was an option, or chose a framework that I could write valid mark-up in.

Since I'm guessing neither of those is an option you could go to:

Resharper -> Options -> Code Inspection -> Settings

Look for the section under the heading Elements to skip - Either find File masks and add *.html (or whatever other file extension you might be using) or find Files and folders and mark the specific files/folders that you don't want Resharper to look at.

I want to suggest a better alternative. Instead of skipping inspections of all *.html files it should be possible to just ignore the inspection for Unknown Tags: