Mandatory Feild doesn't work


I Have a problem with the mandatory fields on my website.

When i tried to send a message to the website through the contact us page there is around 6 mandatory fields, but even if i left them empty and submit my message nothing will tell me that there is an error.

Instead, it will show me a message saying that “Thank you for contacting us. We’ll answer you at first opportunity”.

The same problem exist on the Apply for a vendor account page that will allow any one to apply for that account even if he/she submit his/her email only.

How can i solve that?

Thanks in advance.