The "COMMENT" tag or
<!--YouCanPutAnyWordsHere-->
<FONT SIZE="3" COLOR="#FF0033" FACE="ARIAL,GENEVA">
<!FONT SIZE="3" COLOR="#FF0033" FACE="ARIAL,GENEVA">
It allows you to "delete" a tag, without actually removing it, and to re-instate the tag by simply removing the exclamation point.
The "COMMENT" tag doesn't do anything, which is the whole point. Browsers ignore it. Therefore it is very helpful in allowing you to make notes within your HTML document (web page).
The format is simple:
You can put any letters, words or characters where the "XXX" is. This is helpful if you are writing HTML code.
This is the example with color.
<!--XXX-->
You can put a note to yourself, in the code, knowing that it won't show up on the webpage.
For example:
<!--##### Put the new Java applet here ####-->