You’ve probably seen many references to HTML5, along with mentions of certain features being “Deprecated” or “New” in HTML5. This can sometimes be confusing, as you find out that the way you thought you were “supposed” to do something is now not the right way at all.
It can also be annoying — especially since most of these “deprecated features” still work on most browsers. Why bother learning a new way of doing something if the old way works just fine?
And, of course, it can be difficult to find the right information sometimes. Content on the internet doesn’t live forever… but almost. And the older content is, the more likely it is that you’ll find it on a search engine. (All things being equal, Google and the others prefer older content. Also, older content has had more time to acquire backlinks.) This means that you will often find out-of-date tutorials when you are looking for information about HTML.
This article should clear up some of that confusion and get you on the right track with modern web development.