Mandatory Field is Not Working When i close my Form

Dear All,

For Sample : 

 Sales and marketing/Common/Leads/All leads

click create new

Subject & Name is mandatory Field

If u close that form before Fill the mandatory Filed it shows

"Field 'Subject' must be filled in."

When i close my Details Form, its not working
9 mandatory Fileds in My Table which is used in my form

Thanks in advance.........