Sometimes, you put a script in a certain place in a document for a certain reason. For instance, the following script adds the current time and date at the specific point in the document:

<SCRIPT
 TYPE="text/ecmascript"
 LANGUAGE="JavaScript"
>
<!--
today = new Date();
document.write("The time right now is " + 
               today.toString())
//-->
</SCRIPT>

Other script might do things that are not related to the document itself, such as set up event handling. If a SCRIPT element has the DEFER attribute, it indicates that the script contained or linked in that element does not have to be executed immediately. Although this is a nice addition to HTML 4.0, to my knowledge it is as yet unsupported by any browser. However, if you insert scripts that can be executed later on while the rest of the document is rendered, use this attribute, since it has no adverse effects.