Way to do content adaptation to mobile

I creating a site and want turn it mobile ready, i see people talking about very very old technology but everything looks walking to an web mobile experience

I see people talking about frameworks] to mobile web development, also a friend told me about (wurfl)('http://wurfl.sourceforge.net/java/wall.php) to detect mobile features and build an apropriate css file doing content adaptation.

I see people defining three or four css files and using media queries to match device by screen size with responsive fluid design, someone told me that you cant create one content because flow is different in web and in mobile but cant see why!

I need to know if there is some css trick to make one page (load) some images in desktop plataform and (dont load)/(load another) in mobile in a progressive enhancement way, but someone here:

What's the most efficient way to hide content for a mobile version of a site?)

is saying that with css trick images are only hidden but are still requested from the server.

Is really necessary an mobile url version to same content ?

I will build using asp net mvc and IIS/ASP/ASP.net: How to structure web-site to expose mobile version recommends using different views.

Is this necessary ?

Im really a newbee in mobile development and need some advice on the best method to create a mobile version of an existing MVC website.

Thanks

Since you're using MVC I would highly recommend using jquery mobile as well. I've recently worked on a project using MVC, Razor, FiftOne.Foundation and jquery mobile. Using razor views you can change the view being displayed by detecting if the browsers user agent reports that it's a mobile device. This way you don't have to change URLs MVC simply renders a different view.

I'll have to look for the tutorial I found and post a link to it

edit: Found it: Using 51Degrees.Mobi Foundation for accurate mobile browser detection on ASP.NET MVC 3