Comments are of two kinds: again, if you're a C or C++ programmer, you'll recognize them:

//  This is a single line comment - it applies only to a single 
//  line, and the comment is terminated by the end of the line

<?php include("part.hpml"); ?> //  with code is okay too

/*  This is a multi-line comment: once you have started this type of 
    comment, everything following it is commented out until you end
    the comment with this: