Information Technology Reference
In-Depth Information
Although most of this activity happens automatically, you usu
ally can employ one countermeasure. In particular, browsers nor
mally have a setting to turn off JavaScript or other scripting lan
guages. If these languages are disabled, then your browser will
format the HTML it receives, but it will ignore any requests to run
scripts. In particular, turning scripting off will prevent the appear
ance of any popup windows (as well as eliminate ad animation and
the creation of new windows for advertisement). On the other hand,
turning off scripting also will turn off all error checking in forms
and other aids that you might find helpful. It is technically possible
for browsers to allow you to run a scripting language but block pro
cessing related to new windows. However, details of such an op
tion, if available, would depend on your specific browser.
As a practical matter, some people have concerns that script
ing also may allow Web developers to take advantage of security
problems in a browser, and thus open up a user to destructive or
annoying programs. I would estimate that approximately one
fourth of educational computing professionals routinely turn off
scripting for security reasons. These people avoid potential annoy
ance, but they also miss helpful features of error checking and
form processing.
As we have already discussed, companies have strong incentives
to publicize their products, so they often want to place ads where
potential customers will find them. In Web applications, this in
cludes paying vendors, such as search engines, to include links to the
commercial sites and display ads within other Web pages. We also
have noted that scripts within Web pages can generate popup win
dows at various times. Because Web developers can control the con
tent of these windows, it is hardly surprising that popup windows
sometimes contain advertising.
The display of these ads may be further refined by two addi
tional factors. First, scripting allows the dynamic display of mater
ial. In particular, scripts can change the appearance of pages over
time. This allows one ad to be replaced by another and also allows
some animation of ads. Second, we have already discussed in
