In this day and age, every website should be optimized for mobile viewing. However, with so many devices available on the market, things can be a little tricky — unless you use a tool like Mobile Emulator.
Page2Images’ Mobile Emulator supports Javascript and Flash and displays results for the Windows Phone, iPhone (4, 4s, 5, 5c, 5s), iPad (2, 3, 4), Android, and BlackBerry.
Visit http://www.page2images.com/mobile_phone_emulator, paste the link to your website in the URL box, choose the device, screen size / orientation, and click the Submit button. The resulting screenshot will appear below. You can then download it.
Note that each screenshot also has a dedicated link for easy sharing.