Take a look at jQuery.browser: http://api.jquery.com/jQuery.browser/
The $.browser property provides
information about the web browser that
is accessing the page, as reported by
the browser itself. It contains flags
for each of the four most prevalent
browser classes (Internet Explorer,
Mozilla, Webkit, and Opera) as well as
version information.
Available flags are:
webkit (as of jQuery 1.4) safari
(deprecated) opera msie mozilla This
property is available immediately. It
is therefore safe to use it to
determine whether or not to call
$(document).ready(). The $.browser
property is deprecated in jQuery 1.3,
and its functionality may be moved to
a team-supported plugin in a future
release of jQuery.
Because $.browser uses
navigator.userAgent to determine the
platform, it is vulnerable to spoofing
by the user or misrepresentation by
the browser itself. It is always best
to avoid browser-specific code
entirely where possible. The $.support
property is available for detection of
support for particular features rather
than relying on $.browser.