Sharepoint internet Site FBA Login is not opening

I have configure sharepoint 2010 Intenet site for our Customers .

I have done all the configuration ref : http://donalconlon.wordpress.com/2010/02/23/configuring-forms-base-authentication-for-sharepoint-2010-using-iis7/

I have 2 seperate web apps one is on 80 and another is on 1004 .The Web Apps which is on 1004 on that I have configure FBA .

My Problem is that the FBA login page is opening in inside the domain but for External User (Internet ) it is Prompted for User Name and Password . I am not able to resolve this issue .

Kindly help ..