You have your screen resolution set to a particular resolution. The people who will be viewing your web site may be using the same or a completely different resolution to view your page. They may also be using a different browser from you and possibly a different operating system.
As a result of this, what they see on their page may be completely different from what you see when you browse your page. Everything may be nicely aligned when you view the page but totally scrambled when someone else views it.
One thing that you can do to reduce this problem is to view your page in a variety of different screen resolutions. This doesn't cover all of the variations due to different browser or operating system but its a start.
You don't want to have to actually change your real screen resolution in order to be able to test your page at different resolutions. All you really need to do is to open your browser window to the various sizes and check the appearance of your page.
It is not obvious when you are changing your browser size as to just how big your browser window is. Also depending on the browser and operating system, the actual viewing area may be less by some amount than the actual screen resolution due to the presence of operating system control bars and the browser menu bar etc.
To resolve this problem for you, I have worked out the maximum amount of space that you can be guaranteed will be available at each of the various common screen resolutions and created links that you can use to open a new browser window of that size. In each case the actual viewable area will probably be smaller than you expect due to the additional overhead required by an operating system or browser different from the one that you are actually using. All you have to do is click the button below that corresponds to the resolution that you want to check and a new window will open at the appropriate minimum size that you can guarantee that people using that resolution will get if they maximize their browser but don't switch to full screen mode.
You can use these browser windows to test your own page at various resolutions. Just open a window of the required resolution then type the address of your web page into the address bar of the new browser window and press enter.
This article written by Stephen Chapman, Felgall Pty Ltd.