Yahoo! have historically been rather lacking in their Mac support. The real-time quote page states:
<pre>SYSTEM REQUIREMENTS
OPERATING SYSTEMS:
Windows 98/2000/ME/XP (Pro & Home)
JAVA ENABLED BROWSERS:
Internet Explorer 5.0 and above
Netscape Navigator 6.0 and above
LATEST JAVA INSTALLED:
The application will download the latest version for you.
We do not currently support Macintosh or Macintosh running Windows XP.</pre>
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