>I have tried:
>"~/MembersOnly/MemberPortal.aspx"
>"MembersOnly/MemberPortal.aspx"
>"../MembersOnly/MemberPortal.aspx"
>
>I can't get anything to work, any help is appreciated.

You should be able to use /MembersOnly/MemberPortal.aspx. You can't use the ~ syntax here since you're not using server-side controls. This assumes that your URL looks like this when you are in the root directory:

http://www.mywebsite.com

If it has a subdirectory, eg http://www.mywebsite.com/POAAEWeb/ then you need to change the links to /POAAEWeb/MembersOnly/MemberPortal.aspx.