yes.... sure he can...

go to settings-->configuration-->general settings

check the Allow external users to sign up  

In form customer, menu More->Portal Access Management. Here you need to give permission to the client. Invitation will be sent.

Before, in menu Settings->General Settings check Activate the customer portal

Thanks for your suggestions but it gave me error when i click on signUP page 

The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.

butt i got it now .SOLEVD... by mistak  i have selected public instead of Template in External users 

Thanks