Website prompting for username and password

Hi Friends,
I'm new to webhosting. I hosted a website few days back. I transferred files using FTP into HTTPDocs folder in the server and the page was visible when i specified the url in the browser. Suddenly, two days back, if I give the url , it is prompting for username and password. I don't know what went wrong and please guide and help me to resolve this issue. Thanks for your help in advance.

Are you still able to access it with FTP?

Yes, I'm able to access it with FTP.

if it is a pop up prompt then you have a .htaccess file there that blocks the access to your files if you have an in page pass request.. then that means that you have restricted the access yourself from the account panel of management.