Sitemap error

When I try to add new sitemap in my admin panel I have this warning:

Warning: file_put_contents(/home/areavis/public_html/sitemap.xml): failed to open stream: Permission denied in /home/areavis/public_html/inc/classes/BxDolSiteMaps.php on line 138

Warning: Cannot modify header information - headers already sent by (output started at /home/areavis/public_html/inc/classes/BxDolSiteMaps.php:138) in /home/areavis/public_html/inc/admin_design.inc.php on line 48

How can I fix this? Please help

 
The error message says whats wrong.

Check the permissions. That file needs to be writable. Mode 777

 Thanks! I change sitemap.xml permission to 777 and works good now.