SharePoint Upgrade from MOSS 2007 to SharePoint 2013

We are upgrading from MOSS 2007 to SharePoint 2013. While upgrading from MOSS 2007 to SharePoint 2013, we are facing an error
“Troubleshoot issues with Microsoft SharePoint Foundation. Correlation ID: 543887d4-d68f-4a1f-81ce-e9bdc8cc569e ...."
We are not able to open our homepage. We have branding on our portal that is custom master page.
Please help ASAP?