Content Management Framework for websites

hi there I am looking for preferably a pre-built content management framework that can be customised to our needs, in ASP or PHP or ASP.NET or if it can handle websites in all 3 that would be a big advantage. If not pre-built then someone or a team of people that can build one for me as soon as possible with fully commented code, documentation on it, and details of how it works (help guide or similar).