OK, this is odd and I am sure I have forgotten something very basic here but...
I created and published a new website using VS2010 with a 'place holder' home page (Home.html) which is so basic it is untrue.
I have set this as the start page in my project and tested it in local-host and the 'Place holder' page renders just fine.
I have published it to our IIS server and when I go to http://url/page.html it works but when I go to http://url/ I get an error 404 page does not exist.
What stupid error have I made? It is set as the start up page in the project.
I have added it as a default document in IIS also even though I don't think I needed to.
I maintain lots of websites but this is the first new one I have published for a while... someone help a forgetful old fool out...!