Consider a printed magazine. Regardless of where the magazine is purchased, the images displayed inside look the same in every copy. In fact, only those who are color-blind or vision-impaired will encounter differences in printed graphics. This isn’t the case with web graphic, because each person viewing a web site is doing so with a different set of experiences, affected by his or her computer, browser, monitor, lighting, and modem, to name a few.

When designing for the web (as opposed to a non- screen-based medium), several issues directly affect the outcome and must be considered:
• Platforms
• Code
• Browsers
• Color
• Bandwidth
• Fonts

Platforms
A person’s Custom web design experience is affected by his or her web platform, or the type of device being used to access the web. While obvious differences exist between computers and mobile phones, both are used to view web pages. Furthermore, many different exist between the types of computers used- for example; consider the differences among handheld computers, laptop computers, and desktop computers.

And among those different types of computers, windows, Macintosh, UNIX, Linux, and many other operating systems are running. Many computers even enable you to surf the web from your television. Undoubtedly, many more such devices are yet to come.

• The most important thing to consider about platforms is that the one you’re using probably won’t be the only one your site’s visitors will use. Here are a few general things to consider when you’re designing for more than one platform:

• Graphic design services generally look darker on most PCs running windows than they do on a Mac, but windows gamma (or business) can vary widely. A graphic that appears fine on one windows PC screen might look much darker on another windows screen with different settings.

• Software (such as browsers, plug-ins, and active controls) available for your platforms might not be available for other platforms.

• The size and setting of the viewing device (be it a 17-inch monitor, a 27-inch TV, or a 2-inch handheld screen) used by your visitors will alter the appearance of your graphics.

Screen size
Many designers choose to begin designing the look and feel of a web page within a design program while others start with pencil sketches on paper. In either case, one of your steps should be to identify the most appropriate size at which to design the page.
I talked about identifying the most common screen area used among your site’s target audience. This meant considering sizes such as 800X600and 1024X768. Unfortunately, making that decision isn’t the final step in the process, because the browser itself, as well as the operating system, also takes up some space on the screen.

You need to consider several things when you look at the usable part of the screen area, including the operating system and the browser itself. The amount of space used by the operating system depends on which operating system is in use and how the user has it customized