Make sure you have uploaded the latest version of the webassist/google_javascript folder. It appears the one that is up is out of date and doesn't have a reference to the map_4 object that you are using.
Also your page has:
<?php include("../webassist/google_javascript/wagmp_map_4.php"); ?>
I think it should be:
<?php include("webassist/google_javascript/wagmp_map_4.php"); ?>
but that file hasn't been uploaded yet.