Some HTML tags like br and hr have no content and cannot have a closing tag. What is the complete set of these tags?
Check the table at http://www.w3.org/TR/html4/index/elements.html.
Look at the 'EMPTY' column here:
Every tag in the DTD that has EMPTY in the fourth field is empty.
http://www.w3schools.com/tags/default.asp
All the one that has a forward slash in their tag name. (correction) thx =O
Html don't force the document to be well formatted, so end tags for certain tags like <br> and <hr> can be left out and still the page loads fine, but it's like they cannot have end tags </br> and <br /> works just fine. There is probably no division like Content and Non-Content tags, Refer to this article for details on Tags http://www.devx.com/projectcool/Article/19816
来源：https://stackoverflow.com/questions/3581066/which-html-tags-have-no-content