must “invent” his tags.

The tags used to mark up HTML documents and the structure of HTML documents is predefined. The author of HTML documents can only use tags that are defined in the HTML standard (like <p>, <h1>, etc.).

XML allows the user to define his own tags and document structure.

4. XML Tags are Case Sensitive

Unlike HTML, XML tags are case sensitive. In HTML the following will work:

<Message>This is incorrect</message>

In XML opening and closing tags must therefore be written with the same case:

<message>This is correct</message>

5. XML Elements Must be Properly Nested

Improper nesting of tags makes no sense to XML.

In HTML some elements can be improperly nested within each other like this:

<b><i>This text is bold and italic</b></i>

In XML all elements must be properly nested within each other like this:

<b><i>This text is bold and italic</i></b>

6. XML is a Complement to HTML, not a replacement for HTML.

It is important to understand that XML is not a replacement for HTML. In Web development it is most likely that XML will be used to describe the data, while HTML will be used to format and display the same data.
Syntax Rules for XML

The syntax rules for XML are very simple and