Our control of web page appearance is limited
Summary: Web designers only have partial control over what visitors will see.
The source of these limitations can be grouped in three areas: user settings, hardware limitations, and software limitations.
The solution is to use web standards to create designs that display gracefully without worrying about minor deviations.
Limitations caused by user settings
Users can change many aspects of the graphic display to meet their specific needs.
- Visitors can change the size of fonts on your web site by adjusting the "text size" or zoom settings in their browser.
- Users can set the number of pixels shown on their monitor by setting the display resolution of their monitor. This adjustment changes several things, including the size of fonts.
- Users can choose to override your Cascading Style Sheet (CSS) with another file of their choosing. This can radically alter your web site's design, but it allows limited-vision visitors to read your message.
- Web users can control the default size of the browser window simply by dragging an edge or corner. Many visitors choose a size smaller than their monitor's screen size.
- Users can usually change the color depth setting on their graphics system (monitor and graphics circuitry). Settings allow anywhere from 16 colors to millions of colors. Photographs will look more realistic at the higher settings. These different settings use different sets of available colors, making it impossible to specify exactly what colors will be displayed.
- Users can change the monitor's color temperature, color intensity, contrast, lightness, and other settings.
- Even the placement of a monitor and different kinds of room lighting can affect the appearance of your web site.
Of course, many computer users don't know how to change settings, so they use the default settings in their hardware and software.
The equipment your web visitors use may also limit the designer's control over your site's design.
- Some of your visitors won't be viewing your web site on a computer monitor. They might be using a handheld PDA or even a tiny cell phone.
- PCs and Apple Macintosh computers may have different standards for the number of pixels per inch, resulting in images and text appearing smaller on some Macs.
- PCs and Macs also use different target levels for "gamma." (Gamma is a measure of the brightness of the mid-tones of an image.) Images that look slightly dark on a PC will probably look too light on a Macintosh. There's no perfect compromise.
- There are different kinds of monitors, including CRT and LCD. Your site will look a little different on each kind of monitor.
- Different monitors have different abilities in rendering color hue, intensity, and brightness. Low-priced monitors, for example, often make images excessively contrasty and dark. An old monitor may display images very differently than a brand new one.
- The number of colors a monitor can display is determined by the computer's monitor and graphics circuitry. As described above, it is impossible to specify a color. The graphics system approximates requested colors, according to the set of colors available.
- The maximum window size depends on the size of the monitor. The possibilities range from tiny to huge.
- The human body may not be "hardware," but it's worth remembering the impact of individual differences. A significant number of people, for example, have some kind of color blindness. They can't distinguish between colors that would be obviously different to most people.
The software your visitors use will affect the display of your web site.
- Although Microsoft's Internet Explorer is the most popular web browser, there are many others in use. Each browser interprets differently the code that controls the display of web pages. Even colors are rendered differently by distinct browsers.
- Visitors who access your site using AOL's browser will probably view compressed versions of your images. Most AOL subscribers do not know the images they see have been altered or that they could opt out of this default setting. AOL does this to reduce their expenses, but the reduction in quality can dramatically change the appearance of your site.
- Normally, the only fonts available for display will be those fonts which are loaded on users' machines. Different fonts will be available on any one computer, depending on which operating system and software have been installed. There are very few fonts you can assume will be available.
How to design for differing display conditions
Shoddy approach: Simply ignore the problem
Web designers who ignore these limitations often assume that their display situation is "normal." These designers are surprised when they learn that their designs are broken in other situations.
There is no "normal" on the web.
A responsible web developer will test a new web site under a variety of display conditions to ensure that the design works as expected.
Poor approach: Write different code for different situations
In the first years of this decade, many web developers created web sites that provided distinct code for different browsers and systems. For example, an Apple Macintosh using the Netscape 4.76 browser might receive one set of files, but a PC using Internet Explorer 5.0 would receive another.
The problem with this approach is that there are too many combinations of different browsers, systems, and settings to be able to design a solution for each possibility.
Over time the number of combinations increases, requiring that the code be updated to accommodate the new situations. Creating and maintaining all those options wastes your time and money.
Best approach: Use techniques that adapt well over most potential conditions
When used skillfully, using the advanced techniques promoted by web standards can provide relatively tight control without requiring special code for every different situation. An example would be such as using Cascading Style Sheets (CSS) for page layout.
The goal should be to eliminate significant problems but to expect slight deviations in display.
The main disadvantage with this method is that very old browsers generally display only the text and images, without the sophisticated graphic layout. Advantages include faster development times, code that downloads more quickly, and "forward-compatibility" (meaning that the code will work well in future browsers and systems).
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