the problem in the code:
<input id="Full_Name" name="Full_Name" type="text" value="<?php echo((isset($_GET["invalid"])?ValidatedField("form2","Full_Name"):"")); ?>" class="formTextfield_Large" tabindex="1" onblur="hideServerError('Full_Name_ServerError'), if(this.value==''){this.value='Your Full Name'};"/>
is that you are using a comma between the on blur functions:
onblur="hideServerError('Full_Name_ServerError'), if(this.value==''){this.value='Your Full Name'};"
it shgould be a semi colon:
onblur="hideServerError('Full_Name_ServerError'); if(this.value==''){this.value='Your Full Name'};"
use:
<input id="Full_Name" name="Full_Name" type="text" value="<?php echo((isset($_GET["invalid"])?ValidatedField("form2","Full_Name"):"")); ?>" class="formTextfield_Large" tabindex="1" onblur="hideServerError('Full_Name_ServerError'); if(this.value==''){this.value='Your Full Name'};" onfocus="if(this.value=='Your Name:'){this.value=''}" />