the issue is caused by the use of the virtual function for including the validation toolkit files.
change the first 2 lines:
<?php virtual("/WA_ValidationToolkit/WAVT_Scripts_PHP.php"); ?>
<?php virtual("/WA_ValidationToolkit/WAVT_ValidatedForm_PHP.php"); ?>
<?php require_once("WA_ValidationToolkit/WAVT_Scripts_PHP.php"); ?>
<?php require_once("WA_ValidationToolkit/WAVT_ValidatedForm_PHP.php"); ?>
In your site definition go to the Local Info tab.
there is a setting here for "Create Links relative To;"
If you select Site, Dreamweaver will use the virtual function to include files.
If you select Document, Dreamweaver will use the require_once function.
the virtual() function is problematic. It is only supported in a very few servers, where it is supported, it cases output to be added to the header causing the headers already sent error.
you should change the "Create Links relative To" setting to document so that Dreamweaver will always use the more widely supported require_once function.