XHTML Tag Nesting Rule, Learn XHTML online for free, Free online Extensible HyperText Markup Language Tutorial...

<strong><em>This text is bold and italic! </strong> </em>

The above code is invalid in XHTML. XHTML nesting rule dictates that the elements or tags must be properly nested i.e. the element that is opened last, in nesting, has to be closed first. The correct XHTML version of the above code example is:

<strong><em>This text is bold and italic! </em></strong>

It is very common to make mistakes in nesting lists. For example consider the following HTML code example:

<ul>
  <li>Rice</li>
  <li>Meat
    <ol>
      <li>Beef</li>
      <li>Mutton</li>
    </ol>
  <li>Wheat</li>
</ul>

The above code displays properly in most of the web browsers, but the same is not valid XHTML. Note that in the third line of the above HTML code </li> is missing. The correct HTML code is as under:

<ul>
  <li>Rice</li>
  <li>Meat
    <ol>
      <li>Beef</li>
      <li>Mutton</li>
    </ol>
  </li>
  <li>Wheat</li>
</ul>