If web designers wished to remain true to the spirit of One Web, they needed to provide the same core content at the same url to everyone regardless of their device. At the same time, they needed to be able to create different layouts depending on the screen real-estate available.
The shared illusion of a one-size-fits-all approach to web design began to evaporate. It was gradually replaced by an acceptance of the ever-changing fluid nature of the web.
— Jeremy Keith
from the Resilient Web Design book.