What is Screen Resolution ?
Screen resolution of Display resolution is the number of distinct pixels the device (monitor) can display.
Some standard screen resolutions are 640×480, 800×600, 1024×768, 1400×90, 1600×1200 etc
How to find and how to change my Screen Resolution ?
In Windows go to Control Panel –> Display to view and change your Screen Resolution.
You can also find out your screen resolution with
http://www.whatismyscreenresolution.com/
Online Screen Resolution Checking Tools for Web Designers
Theoretically all web sites should display properly in all screen resolutions, but practically it is not.
So when designing a website, web designer has to check the site in multiple resolutions to make sure that it works perfectly in all screen modes. But it is not easy to change the local resolution setting every time for testing.
This site provides a very easy and convenient methods to test web sites in different screen resolutions.