ddavison,
<a href='~/Member/ContentPage.aspx'> is an application based path. It's an ASP.NET feature. But it only works in server side and it's a invalid path in browsers. When you use it, ASP.NET will convert this path to regular path automatically in server side.
asp.net Chat http://cutesoft.net/ASP.NET+Chat/default.aspx
Web Messenger: http://cutesoft.net/Web-Messenger/default.aspx
asp.net wysiwyg editor: http://cutesoft.net/ASP.NET+WYSIWYG+Editor/default.aspx
asp wysiwyg html editor: http://cutesoft.net/ASP
asp.net Image Gallery: http://cutesoft.net/ASP.NET+Image+Gallery/default.aspx
Live Support: http://cutesoft.net/live-support/default.aspx