When I did a fresh install of Mandrake 8.2 with Apache I got this error when trying to access my websites that I had stored on another drive. I was upgrading from NT 2000 using IIS 5.0 so I had my original websites that were working before stored on another drive.
I spent 3 days looking for a solution to the 403 error I was getting when I tried accessing my websites. I had everything setup correctly in Apache (at least I thought). And I kept dinking arounf with my virtual server settings. I even changed the path in Apache for my default website to make sure it was not a webpage error.
My website pulled up fine when I did this but even though I duplicated the settings in my default site with the new Virtual site I created for my website I still got a 403 error.
The solution: You need to make the changes in the directives.
Once I added lines to my commonhttpd directive in Apache for my vitual server and the path where my websites were located I was then able to pull up my websites without this error showing up anymore. I have more information about the steps you go through to do this on my website.
I hope this helps others who maybe having the same problem I was.