make sure that all of your form elements have a propper type attribute on them:
for example:
<input type="text" name="element" id="element" />
if there are any elements that do not have a proper type attribute:
<input name="element" id="element" />
or the type is left bkank:
<input type="" name="element" id="element" />
this is not valid html and will produce the error you are reporting.