The Responsinator helps website makers quickly get an indication of how their responsive site will look on the most popular devices. It does not precisely replicate how it will look, for accurate testing always test on the real devices.
We recommend using Chrome on OSX Lion with scroll bars set to "when scrolling" (System Preferences › General › Show scroll bars › "when scrolling"). This means the device widths aren’t affected by scroll bars.
Tags: emulator, mobile, iphone, apple