Optimizing
Images for the Web - Part III
by Charles E. Brown
Performance
Considerations
Taking Control of your
Images
If Web performance (time it takes a page
to load) is to be improved, two primary factors are to be considered,
#1) the speed of the Net connection and #2) the amount of data that
needs to be transferred. There may be a vast number of communications
vehicles in-between the server that houses a page and the browser that
reads it. The slowest vehicle is usually the home connection, which is
typically achieved using a low-speed connection via analog modem and
standard telephone lines. A page that might take a few seconds to load
from work (on a high-speed workstation using a broadband connection)
might take five minutes on a bandwidth challenged home system using a
standard telephone modem. Therefore when a Web author is optimizing
images for the Web he/she must take into account not only the type of
browser (surfboard) the user is surfing with but also the type of
connection (wave) the surfer is riding on.
The 30 Second Rule
Millions of people using the major Online
Services (AOL, Prodigy, exc.) and Internet Service Providers (ATT, Bell,
exc.) are dialing in at speeds ranging from 9,600bps to 56,000bps (bits
per second). It was once believed by Web authors that 30 seconds of load
time for a Web page was a good rule of thumb, however this needs to be
explained further. This does not mean it should take 30 seconds for
something to appear on the display, this means 30 seconds to download
the entire page (all content). The user should see text before the page
has completely loaded. All relevant text should appear on the display
before the first 10 seconds have expired and all small images (5k and
under) should be displayed before the 20 second mark. The Web is the
domain of the attention deficit populous of the right-here and
right-now. After 30 seconds, all bets are usually off as to gaining and
keeping their attention. If the user did not get what they were looking
for or at least a pleasant surprise that was unexpected, they're gone.
However the 30-second rule does not take into account Net congestion or
overloaded servers.
The Two Screen Rule
Web authors have another rule of thumb that suggest that you
should not put more than two screens worth of information on one HTML
page (the amount of information that two screens constitutes will vary
with font size, monitor size and screen resolution). HTML markup and text
should load in much less than 30 seconds, but inline images on your page
may take longer. Tuning these images can significantly impact the transfer
speed of your page.
Go to Optimizing Images for the Web
Part IV
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About the author...
Charles Brown is a freelance writer specializing in Internet and
consumer related articles. He is also a content
writer for EWM / PSI (Everyone Working Mutually providing
Products Services & Ideas). Mr. Brown is also the
author of a new series of eBooks that will begin publication in
mid February, 2001. "The Art of Complaining © 1998
Charles E. Brown" will be a how-to on writing effective
letters of complaint. "The Art of eShopping © 2000 Charles
E. Brown" which will be a how-to on safe and efficient
internet shopping. Scheduled for publication in
July/August, 2001are "The Art of Web Design © 2000 Charles
E. Brown" and "The Art of Desktop Publishing © 2000
Charles E. Brown".
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