HTML5 is the latest HTML standard. Sooner or later, all web programmers will find that they need to use this latest standard. Moreover, many people will feel that it is more difficult to redevelop a website with HTML5 than to develop a website. Migrating from HTML4 to HTML5 is much easier because there are significant differences between the two versions.
In fact, HTML5 does not make any major changes to HTML4. Many of them are similar.
However, there are some important differences you need to know. Listed below are some of the main differences between HTML4 and HTML5 (not all, it is impossible to list them all):
1. The HTML5 standard is still being developed
This first difference is obvious, but so important that I need to start with it. Maybe you've noticed that there's a lot of talk about how cool HTML5 is, but the reality is that HTML5 is an unfinished standard. HTML4 is already 10 years old, but the fact that it is still the current official standard has not changed.
On the other hand, HTML5 is still in its early stages, and future modifications will continue to appear. You must take this into consideration, because the newly added or modified web elements you use on your website will change every year, and you need to constantly update and upgrade your website, which is not what you want. This is why, for now, you're better off using HTML4 in production and only using HTML5 in experiments.
2. Simplified syntax
Simpler doctype declaration is one of the many new features in HTML5. Now you just write and that's it. The syntax of HTML5 is compatible with HTML4 and XHTML1, but not SGML.
3. A new
For Web users, Flash is both a surprise and a pain. There are many web developers who are dissatisfied with the threat HTML5 poses to Flash. But for those of you who put up with bloated Flash videos that took years to load and run, the technology to generate videos with the new