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774 WEBSITEDESIGNGraphics
The two major interface issues concerning graphics are
size and color. As the majority of Web users still access
Web sites over slow modem links, it is important to use
graphic images that are of reasonable size, to prevent
excessive download delays. For photograph images, the
JPEG format offers a good compromise between lossy
compression size and image quality, with an adjustable
tradeoff point. For line art and solid color images, lossless
compression is preferred, and the proprietary GIF format
is common, although the open standard PNG format is
gaining in acceptance (Roelofs, 2000).
The issue of colors is a complex one and depends on
many factors. In general, Web graphic designers work
with 24-bit colors, with 256 possible values for each of
three color channels, red, green, and blue (RGB). Until re-
cently, the majority of users’ computers and Web browsers
could only support a palette, or set, of 256 colors simul-
taneously. To ensure that colors appear uniformly across
platforms and browsers, a “Web-safe palette” of 216 colors
was established, consisting of combinations of six pos-
sible values, or points, for each of three color channels
(6 possible reds×6 possible greens×6 possible blues=
216 possible colors) (Niederst, 2001).
Recently, browsers and systems with 24-bit and 16-bit
support have drastically increased and now account for
about 94% of all users (Lehn & Stern, 2000). Twenty-four-
bit color support results in the full display of the designer’s
color scheme. Sixteen-bit color systems are sometimes
problematic, as they nonuniformly sample the three color
channels (5 bits for red, 6 bits for green, and 5 bits for blue)
and provide a nonpalettized approximation of 24-bit color.Layout Styles
A comprehensive guide to layout styles is beyond the scope
of this chapter. The major design decision is between hav-
ing page layouts of fixed or variable size (Niederst, 2001).
By default, HTML documents are variable-sized, in that
text and graphics positioning and line breaks are not deter-
mined by the user’s monitor resolution and browser win-
dow size. Since a wide variety of sizes and resolutions is
almost a given, having a variable-sized page layout allows
flexible designs that scale to the capabilities and prefer-
ences of each user. The disadvantage is that because each
user experience is different, and elements can be resized
or repositioned at will, it is difficult to design a consistent
and coherent interface; there is the possibility that some
configurations lead to poor or unusable interfaces.
The alternative to the default variable-sized page lay-
out is to explicitly design the size and position of some
or all of the elements of a Web document. An example of
this would be to limit the width of all content in a page
to fit within a certain horizontal screen resolution, such
as 640 pixels. All text and graphics will remain stationary
even if the user resizes the browser window to greater
than 640 horizontal pixels. The advantage of this method
is that designing an interface is much more deterministic,
so the Web designer will have some degree of control over
the overall presentation and is reasonably certain that all
users will have the same experience accessing the site.
The disadvantage is that the designer must pick constantsthat may not be pleasant or valid for all users. For ex-
ample, a Web page designed for a 640×480 resolution
screen will look small and limited on a 1280×1024 screen,
whereas a Web page designed for an 800×600 screen
would be clipped or unusable for users with only a 640×
480 screen.
Actually implementing either type of page layout can
be done with HTML frames, tables, or CSS style sheets,
or some combination of the three. Although using style
sheets is the currently preferred method for page lay-
out, browser support is still poor, and many sites still use
frames or tables (Niederst, 2001).Search Engines
A search engine is a useful tool to help users quickly
find particular content or page as the content of a Web
site increases, or the navigation scheme becomes com-
plicated. The search engine is a server-side software pro-
gram, often integrated with the Web server, that indexes
a site’s Web content for efficient and quick retrieval based
on a keyword or phrase. Search engines are available with
a variety of configurations, interfaces, and capabilities.
A good resource that summarizes the major commercial
and open source engines is the Search Tools Web site
(http://www.searchtools.com).Cross-Browser Support
Designing a Web site that is consistent across multiple
browsers and platforms is one of the most challenging
tasks a developer faces. Even different versions of the
same browser are sometimes incompatible. At the mini-
mum, the three major browsers to consider are Internet
Explorer (IE), Netscape Navigator (NN), and text-based
browsers such as Lynx.
For the most part, browser development and capabili-
ties have preceded the establishment of formal standards
by the W3C, leading to numerous incompatibilities and
nonuniform feature support. The latest versions of the two
common browsers (IE 6, NN 6.2) offer complete support
for the current W3C standard HTML 4.01. However, the
more common, earlier versions of the browsers (versions
4 +and 5+) had only incomplete support.
Even more troublesome was their support of the W3C
standard Document Object Model (DOM) Level 1, as each
has historically taken a different track and implemented
its own incompatible DOM features (Ginsburg, 1999).
In general, NN’s DOM support is much closer to the
“official” W3C DOM Level 1 specification, whereas IE has
several extensions that are more powerful, but are avail-
able only on Windows platforms. The latest versions of the
two browsers have alleviated some of this problem by sup-
porting, as a baseline, the complete Level 1 specification.WEB RESOURCES
Table 1 summarizes some useful online resources for Web
site development. They are only suggestions and should
not be considered comprehensive or authoritative.CONCLUSION
This chapter has given an overview of Web site develop-
ment, including the design and implementation aspects.