HTML 4.01 & HTML 5: deprecated and not supported tags

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As you may already know we are near the introduction of HTML 5, even if it is not a W3C recommendation yet. It is quite clear that browsers will not stop understanding HTML 4.01 tags, probably for a long time, however it is time to start thinking about what will be or it is already deprecated in HTML 4.01 and HTML 5. The new version will improve "interoperability and reduce development costs by making precise rules on how to handle all HTML elements, and how to recover from errors.
Some of the new features in HTML5 are functions for embedding audio, video, graphics, client-side data storage, and interactive documents. HTML5 also contains new elements like <nav>, <header>, <footer>, and <figure>.
The HTML5 working group includes AOL, Apple, Google, IBM, Microsoft, Mozilla, Nokia, Opera, and many hundreds of other vendors." (quoted from W3C web site)
That is actually very interesting, but it could pose some issues. In fact, if you think about the code you wrote in the past years, it could be that many times you used already deprecated tags. That means you should go back and change all your code. HTML 5 ready browsers will continue to interpret old tags, otherwise millions of web sites would stop working correctly. And nobody wants that to happen.
So, you can still sleep tight, however it is important to know what will happen.

What is already deprecated in HTML 4.01

In HTML 4.01 some tags are already deprecated, even if - I bet - many web developers still use them. First of all I must say that the reason why some tags were "removed", is the introduction and the will to improve the use of CSS style sheets. In fact many deprecated tags can be easily replaced by appropriated styles.
This is the list of HTML 4.01 deprecated tags:

• <applet>
• <basefont>
• <center>
• <dir>
• <font>
• <isindex>
• <menu>
• <s>
• <u>
• <xmp>

I am sure some of you (me included) know that somewhere in old web pages, those tags are used. Well, I believe you shouldn't bother too much.

... and HTML 5?

In HTML5 some other tags will be "not supported". It is not a big deal, anyway it's worth knowing which are those tags:

• <acronym>
• <applet>
• <basefont>
• <big>
• <center>
• <dir>
• <font>
• <frameset>
• <noframe>
• <strike>
• <tt>
• <u>
• <xmp>

What's new in HTML 5?

You might wonder what tags will be introduced in HTML 5. Well, just for the sake of completeness, here you are:

• <article>
• <aside> 
• <audio> 
• <canvas> 
• <command> 
• <datalist> 
• <details> 
• <embed> 
• <figcaption> 
• <figure> 
• <footer> 
• <header>
• <hgroup> 
• <keygen> 
• <mark> 
• <meter> 
• <nav> 
• <output> 
• <progress> 
• <rp> 
• <rt> 
• <ruby> 
• <section> 
• <source> 
• <summary> 
• <time> 
• <video> 
• <wbr> 

Go to the W3C page for more information.

I believe that many of the "new" tags will soon be marked as deprecated (maybe in HTML 6). However, I leave the comments to you in the section below.