exporting and importing users by cvs file

hi

I am in upgrading the site and deleting old files from host ... 

to renew my site >>> I changed my old site to a development site ( subdomain ) ..

I checked the members > browse users in admincp ...I exported users in cvs format file there, ( option that is right above the window ) ... and now I want to import uses ( by cvs file ) to new site ... but new site does n,t accept the cvs file and alarms :  " File must be include 3 required fields: full_name,user_name,email " in a red colour box ! I cheked the file, there has wrote these options for users!

what can i do?