Multiple urls for multiple clients same website

Just wondering if this scenario is possible:
If v have multiple clients say ClientA, B… n
each client will use their url and so on
and log into their url/site.
Only the header & footer will be different for each client but the functionality
in the middle pane will be same with different data for each client.
Is it possible to setup urls and load differently for each of them.
Please share your thoughts & suggestions.
Help much appreciated.