If you have a website, it is imperative to make sure it looks right on a small screen. While you can use a smartphone to do that, there is an easier way. If you have a Google Chrome browser, open a website, just like you usually do. Then press the F12 key on your keyboard, which will open the developer tools panel. If it is your first time using it, it will probably be docked to the right side of a screen. Once it is open, you will see an icon of two devices on the top left corner of the panel. If you click on it, you will toggle the device toolbar. This creates a frame around your website, and you can quickly test it at any width. If you want to test your website on a specific device, you can choose it from the drop-down list. But generally, you should test the range from 360 to 420 pixels since they are the most common mobile screen sizes.