All the executable content elements we’ve discussed so far have had one common trait: they are separate from the browser and the HTML/XHTML document—separate data, separate execution engine.
the HTML and XHTML standard
The browser processes everything between
statements and data. You cannot place HTML or XHTML within this tag;
the browser flags it as an error.
However, browsers that do not support
<script> process its contents as
regular HTML, to the confusion of the user. For this reason, we
recommend that you include the contents of the