Are custom elements valid HTML5?

Question

I\'ve been unable to find a definitive answer to whether custom tags are valid in HTML5, like this:

Hello!

Answer 1

I know this question is old, but I have been studying this subject and though some of the above statements are correct, they aren't the only way to create custom elements. For example:

click me

I won't be displayed :D

would work perfectly fine ( in newer versions of Google Chrome, IE, FireFox, and mobile Safari so far ). All you need is just an alpha character (a-z, A-Z) to start the tag, and then you can use any of the non alpha characters after. If in CSS, you must use the "\" (backslash) in order to find the element, such as would need Query\^ { ... } . But in JS, you just call it how you see it. I hope this helps out. See example here

-Mink CBOS