Please validate the following code: 
 
  body { 
    font-family: Arial, Helvetica; 
    font-style: underline; 
    margin-left: 6px; 
    margin-right: 5px; 
    text-indent: 9px; 
  }
Post your results and offer an
explanation of what - if anything -
needs to be corrected.

Results from W3C validator:
Errors
URI : file://localhost/TextArea
Line: 0 Context : body 
Invalid number : font-styleunderline
is not a font-style value : underline 

Warnings
URI : file://localhost/TextArea
Line : 0 font-family: You are
encouraged to offer a generic family as
a last alternative
Valid CSS information
body {
font-family : Arial, Helvetica; 
margin-left : 6px; 
margin-right : 5px; 
text-indent : 9px; 
} 

Modifications:
1. Use shorthand to shorten font
statements
2. correct the font style, change to
text decoration
3. Add a generic font family
body { 
    font-family: Arial,Helvetica, sans-
serif;
    margin-left: 6px; 
    margin-right: 5px; 
    text-indent: 9px; 
    text-decoration:underline;
  }

This validated with no error or
warnings.

Convert the following STYLE
definitions so that the headings look
similar using em for the unit of
measure instead of pt. 
 
  <style type="text/css"> 
    <!-- 
    h1, h2, h3, h4 { 
    font-family: Arial, Helvetica,
sans-serif; 
    font-style: italic; 
    color: #000080; 
    background: #00ff00; 
    text-decoration: underline; 
    } 
    h1 { font-size: 30pt; } 
    h2 { font-size: 22pt; } 
    h3 { font-size: 16pt; } 
    h4 { font-size: 12pt; } 
    --> 
  </style>
* Please include the browser and
operating system you are using.  For
example: Netscape 7.1 in Windows XP. 
If you know your screen resolution post
that too.

For answer, see
http://users.erols.com/berke/CSS/UsingEm
2.html
Except for heading 4, the results are
identical regardless of unit used. This
is probably because one em equals 14
points, and the point size of heading 4
was 12 pts, or less than one em.


Many people prefer to use pt as a unit
of measure for font-size rather than em
or percentage.  What advantages or
disadvantages can you see to using pt? 
What advantages or disadvantages can
you see to using em?


According to the lecture table, pt is
an absolute unit while em is relative.
Recall that absolute does not scale,
and relative does scale well. 
For this reason you have to avoid
using a point size too small or it
won't display in a readable format on
say a Macintosh).
Also, according to
http://www.htmlhelp.com/reference/css/u
nits.html,
a relative unit like em is preferable
because it will adjust better to
various media (pretty important when
you consider the popularity of
handhelds and wireless access devices).
If I changed the default font size for
my browser, a page using Ems instead of
an absolute value, would probably
reformat better. 

Also note the definition of an em is
"the height of an element's font." That
means that if I want to make a letter
tall compared to the rest of the text
in a paragraph, I'm better off using an
em instead of a pt.
If I'm only using em/pt to control how
big text looks on a page, I don't see
any harm in using either one as long as
I make sure not to use a too-small
point(absolute) size, but it is clear
that em (or px) is the better choice
for the reasons cited above.

I don't know how the two would compare
using a printer. On page 72 of the
text, it states that points were
developed for printing purposes; so if
you are converting a print document
like a brochure, to the web, I suppose
it would be advantageous to use pt to
mimic the look as closely as possible.
Em is also useful for child elements,
scaling relative to the parent element,
according to the text.

The only possible disadvantage to
using an em
instead of an absolute unit, is the
same thing 
that is the em's advantage: its
ability to scale.
If the user's style sheet or browser
preferences set 
the font size to an unusual size, the
em's size could
produce odd-looking or impossible to
read results after
scaling relatively.

Rewrite the following code using
shorthand properties: 
 
  p { 
    margin-bottom: 10em; 
    margin-left: 15em; 
    margin-right: 20em; 
    margin-top: 5em; 
    color: blue; 
    background: white; 
  }


(Following Trouble)
p {margin: 5em 20em 10em 15em;
	color:blue;
      background:white;
}

This passed the validator.

Convert the following code from
shorthand to longhand: 
 
  p { 
    color: #cc0066; 
    background-color: #ffffff; 
    font: italic small-caps bold 1em
Arial, Helvetica, sans-serif; 
    text-decoration: underline; 
    text-indent: 10px; 
  }

p { 
    color: #cc0066; 
    background-color: #ffffff; 
font-style:italic;
font-variant:small-caps;
font-weight:bold;
font-size:1em;
font-family:Arial, Helvetica, sans-
serif;   
text-decoration: underline; 
text-indent: 10px; 
  }
This passed the validator.

****
Asking questions again...
I am a bit confused here.
I found this tutorial:
http://hotwired.lycos.com/webmonkey/98/
35/index2a.html?tw=authoring

But it says on page 5:
Unlike pixels, users can adjust the
text size in their browsers when you
use ems.

I'm confused because according to the
text, both ems and px are considered to
be
relative units. Why is it that with a
relative unit like px, users can not
adjust
the text size in their browsers, but
with a relative unit like em, users can?