HTML Comment Tags

You can add comments to your HTML source by using the following syntax:

Notice that there is an exclamation point (!) in the opening tag, but not in the closing tag.

Note: Comments are not displayed by the browser, but they can help document your HTML source code.

With comments you can place notifications and reminders in your HTML:

Example

<p>This is a paragraph.</p>

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Comments are also great for debugging HTML, because you can comment out HTML lines of code, one at a time, to search for errors:

Example

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Conditional Comments

You might stumble upon conditional comments in HTML:

Conditional comments defines some HTML tags to be executed by Internet Explorer only.

HTML For Variables

The HTML  element defines a variable.

The variable could be a variable in a mathematical expression or a variable in programming context:

Example

Einstein wrote: <var>E</var> = <var>m</var><var>c</var>².

Result:

Einstein wrote: E = mc2.

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HTML For Computer Code

The HTML  element defines a piece of programming code:

Example

<code>
var x = 5;
var y = 6;
document.getElementById("demo").innerHTML = x + y;
</code>

Result:

var x = 5; var y = 6; document.getElementById("demo").innerHTML = x + y;

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Notice that the element does not preserve extra whitespace and line-breaks.

To fix this, you can put the element inside a 

 element:

Example

<pre>
<code>
var x = 5;
var y = 6;
document.getElementById("demo").innerHTML = x + y;
</code>
</pre>

Result:

var x = 5;
var y = 6;
document.getElementById("demo").innerHTML = x + y;

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HTML For Computer Output

The HTML  element defines sample output from a computer program:

Example

<samp>
demo.example.com login: Apr 12 09:10:17
Linux 2.6.10-grsec+gg3+e+fhs6b+nfs+gr0501+++p3+c4a+gr2b-reslog-v6.189
</samp>

Result:

demo.example.com login: Apr 12 09:10:17 Linux 2.6.10-grsec+gg3+e+fhs6b+nfs+gr0501+++p3+c4a+gr2b-reslog-v6.189

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HTML For Keyboard Input

The HTML  element defines keyboard input:

Example

<kbd>File | Open...</kbd>

Result:

File | Open...

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HTML Computer Code Formatting

HTML normally uses variable letter size and spacing.

This is not what we want when displaying computer code.

The , , and  elements are all displayed in fixed letter size and spacing.