Exactly the same Xhtml displays differently depeneding on hostname

Question

I have a web page.

When I view it under localhost it looks ok e.g. http://localhost/MySite/ is fine

When I view it using the specific name of my machine one of the pages renders incorrectly e.g. http://MyMachineName/MySite/

However the Xhtml is identical. This makes no sense to me.

(IIS 5/ASP.NET 3.5/XHTML Transitional)

Answer 1

Based on the comments above.

Make sure compatibility mode is set for both localhost and the machine name.

(this answer is just for others who may come across this question. The OP solved this themselves)