RWD Viewport
The viewport is the user's visible area of a web page.
Responsive Web Design - The Viewport
The viewport is the user's visible area of a web page.
The viewport varies with the device, and will be smaller on a mobile phone than on a computer screen.
Setting The Viewport
HTML5 introduced a method to let web designers take control over the viewport, through the <meta> tag.
You should include the following <meta> viewport element in all your web pages:
<meta name="viewport" content="width=device-width, initial-scale=1.0">