Web users across the world may be working on different display screen resolution, so it is better for webmasters to test their websites across all the different resolutions so that they can modify their websites so that it can render properly on different resolutions.
DiffRes Web Page Preview Tool is a free to use program to preview any website across different screen resolutions or screen sizes.
As shown in the above screenshot, you can test website in the following screen resolutions 800 x 600, 1024 x 768, 1152 x 864, 1280 x 720, 1600 x 1200, 1920 x 1140, 2048 x 1536 – this tool seems to be great desktop app to check the websites on different screen resolutions.
However, if you don’t want to use this desktop based app for testing your website, you can try other online tools which lets you do the same. Some of the online tools which could be best to use for this purpose would be Screen Resolution, ViewLike.us etc or else you can try some other utilities also like Sizer for windows.