Datasheet

28
Part I: Programming with JavaScript
Figure 1-12:
The HTML
Validator
extension
adds very
useful
features to
the View
Source tool.
View Source window
Validator errors appear in this window.
The Validor extension provides helpful error messages.
Firebug
The Firebug extension is one of the most important tools in Web develop-
ment. It turns Firefox into a complete debugging tool. Firebug has several
especially useful features:
✓ Inspect Window: This incredible tool allows you to move your mouse
over any element in your page and instantly see the code that created
that section in another panel. This is a very easy way to analyze and
debug pages. You can also see instantly what CSS applies to a particular
snippet of code, and highlight code to see the corresponding output.
✓ CSS View and Edit: You can look over the CSS of your page in a panel,
see previews of any colors, and edit the values. You’ll see the results in
real time on the page.
✓ JavaScript Debugging: Even pros make mistakes — and up to now, few
debugger tools have been available for JavaScript programmers. Firebug
has better mechanisms for error-trapping than the browsers do, and it
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