This website was created as a tool to provide a visual of your responsive design websites. It displays it in different media size and orientation (portrait/landscape) from an iPhone3 to an IPAD to a Kindle. This website will help you in the design process.
This doesn't subsitute for the real thing, but it comes close. You should test your websites on the actual devices. There's always a variation when testing. Still it is a good tool.
Responsive web design makes your web page look good on all devices. Responsive web design uses only HTML and CSS.
Web pages can be viewed using many different devices: desktops, tablets, and phones. It is called responsive web design when you use CSS and HTML to resize, hide, shrink, enlarge, or move the content to make it look good on any screen.