java version "1.3.1-beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.1-beta-b15)
Java HotSpot(TM) Client VM (build 1.3.1beta-b15, mixed mode)

Java Source Code (Empty.java):
public class Empty { }

Steps to Reproduce:
javadoc Empty

The generated stylesheet.css file contains the lines:
.FrameTitleFont   { font-size: normal; font-family: normal }
.FrameHeadingFont { font-size: normal; font-family: normal }
.FrameItemFont    { font-size: normal; font-family: normal }

These lines generate the following errors when run through the W3C CSS
validator (http://jigsaw.w3.org/css-validator/):
Line: 14 Context : .FrameTitleFont Invalid number : font-size
normal is not a font-size value : normal
Line: 15 Context : .FrameHeadingFont Invalid number : font-size
normal is not a font-size value : normal
Line: 16 Context : .FrameItemFont Invalid number : font-size
normal is not a font-size value : normal
(Review ID: 117336) 
======================================================================
Another submitter:

    http://java.sun.com/j2se/1.3/docs/api/stylesheet.css  references
    font-family: normal in several styles.  This is not correct per 
    w3c spec since normal is not a keyword.  

    I recently added fonts to my system including one named
    "normal" which this stylesheet causes to be used in the javadoc
    left-hand frames.  It is a large and whimsically styled font family
    which is quite annoying in this context.
    Perhaps this should have been
    font-style: normal
    instead.  But in any case please leave off the 
    font-family specification to allow it to default instead of 
    specifying "normal".
    
       xxxxx@xxxxx  

Manually edit the stylesheet.css file each time javadoc is run, and specify the
value "medium" for the font-size property.
======================================================================

It appears from the workaround that this person is asking us to change 
"normal" to "medium".  However, in Netscape on Solaris, this changes the
fonts in the left-hand frame from serif (Times) to sans-serif (Courier).
In this example, the default font in Preferences is Times.
So this is not an acceptable fix.  I'll write to ask him what he suggests.
  xxxxx@xxxxx   2001-02-22

His suggestion is to omit the font-size, since neither normal nor medium
work (would "default" work?), and to change font-family to serif.
Details under "Comment".  My suggested fix is under "Suggested Fix".
  xxxxx@xxxxx   2001-02-23

Assigning to Jamie to implement.  The final file should look like the
attached file stylesheet.css
  xxxxx@xxxxx   2001-03-28

This bug has been fixed in 1.4.0.  The final file now looks like the attached file.  Location of fix:

StylesheetWriter.java

  xxxxx@xxxxx   2001-05-29

I have to reopen this bug because it was not fixed properly.  The new lines in the stylesheet should be commented out (as mentioned in the suggested fix).  Also, pts should be pt in the stylesheet.
  xxxxx@xxxxx   2001-10-26

In addition to the two bugs mentioned above, the word "sans-serif" is
newly misspelled.  It is misspelled "san-serif".  

  .FrameTitleFont   { font-size: 10pts; font-family:
  Helvetica, Arial, san-serif }

Should read:

  .FrameTitleFont   { font-size: 10pt; font-family: 
  Helvetica, Arial, sans-serif }

  xxxxx@xxxxx   2002-07-08

The point of setting the font size is to make the font in the left-hand
frame smaller, so more characters of a long word are visible.  I suggest making
the font size relative, rather than just choose 10pt.  A value of 80% seems
good.

  xxxxx@xxxxx   2002-08-28

80% was too small for Internet Explorer, so I changed it to 90%
No regression test supplied, because the original problem was just a typo 
in the source.
  xxxxx@xxxxx   2002-09-11

In 1.4.0, the same lines in stylesheet.css are now invalid
for new reasons:  the size is "10pts" instead of "10pt" (why
is it being forced to 10 points?), and the last of the
fallback font families is "san-serif" instead of
"sans-serif".  (Why bother forcing the font family at all?)