Lighttpd static file server 403 forbidden error

You can't access your www folder because www-data user only has 4 right (user:group jurre:www-data and rights 740) which means no execution right on www folder, only read (read folder name and attributes).

You need execution right on folder, because executing a folder means opening it (to list files or to enter it). You can do this with your own user jurre (right 7) but www-data does not have the execution bit set.

Change your right on this folder for 750 and try again.