Mandatory fields don't work

Hi experts,

I need to set some fields as mandatory fields

1. I set the fields as mandatory on HTML5

2. So I created a new account to check if the changes work

And when I saved the new account without complete the mandatory field, in this case City

It allows me to create the account

3. To check the changes via SDK I opened the view Accounts - Quick create

And the changes has no result however I made the changes manually

And when I created a new account again I get the same result, I could create an account without mandatory fields.

Am I doing something wrong?

Please some help

Thanks in advance