Microsoft had released the System Requirements for Dynamics GP 2013, that includes GP Web Client requirements as well. The system requirements page can be found here: System Requirements for Microsoft Dynamics GP 2013.
While I leave it to you to get informed about entire details, it’s worth to brief you about what are NOT supported:
- Windows XP all editions
- Windows Server 2003 all editions
- Internet Explorer 7.0
- Microsoft Office 2007
- Microsoft SQL Server 2005 all editions
- Windows SharePoint Services 3.0
- Microsoft Office SharePoint Server 2007
- Office Communicator 2007
So start planning for the future of GP.