F12 preview connects to server

when i tried to preview a php page DW said it needed to connect to the testing
server ... no problem

however when i preview a normal html page now, it automatically connects to
the server, uploads all related files, and then fails to preview

could some one tell me how to change this option? ive already edited the site
and set testing server to none, but makes no difference

thanks
stef

(sidenote: previewing php and html pages automatically leads me to my server
login page?!)