Media queries plays an important role in Responsive Design. So in that situation the Meta-tag is the one which is most imporatant, <meta name="viewport" content="width=device-width, initial-scale=1.0"> Here Device-width == Content to scale the full width of the device. initial-scale == the Zoom value to view the webpage if the value of initial-scale= 1.0. This is the unscsaled document. if you write user-scalable= "no". Then it disables the zoom.
Be you, The world will adjust