When going to my site FTP Credential screen comes up

I’m not sure what the issue is but sometimes when user or me go to a link on the website the FTP credentials screen comes up?

Screen shot:
http://postimg.org/image/uol4hwlox/

Hi

This issues seems to be related with the permissions set on your wp files. Check this link to set the permissions according with wp-docs: https://codex.wordpress.org/Changing_File_Permissions If this does not work you can also try the solution indicated here as it seems to work: http://stackoverflow.com/questions/21316282/wordpress-plugin-installation-failed-to-connect-to-ftp-server-safest-solutio

Thanks!