Slightly unrelated but this is an awesome picture that I’d love to have a print of. Does anybody know the author or source?

The quote must not be escaped when you start with a single quote. The rest doesn’t. This is valid and tested: <img alt='my "<img>"'>

You can’t parse every html opening tag with regex, because a html opening tag doesn’t have a set structure. How would you match, with regex, this opening tag? <mytag myattribute="<value of \"myattribute\">" >

It can’t be done, as an opening tag in html can contain anything in its attributes, even JavaScript (e.g. onclick handler).