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what's an "em" Re: screen magnifiers and fragmented text

From: Charles McCathieNevile <charles@w3.org>
Date: Fri, 8 Mar 2002 15:09:28 -0500 (EST)
To: Michelle Podd <mpodd@iqnetcom.com>
cc: "WAI (E-mail)" <w3c-wai-ig@w3.org>, David Poehlman <poehlman1@comcast.net>
Message-ID: <Pine.LNX.4.30.0203081500410.24063-100000@tux.w3.org>
It's the size of the letter "m" which is the widest letter in the latin
alphabet (generally).

There is a definition in the CSS specification (lucky, since that is where
the thing is used a lot):
http://www.w3.org/TR/REC-CSS2/syndata.html#length-units
That says "it is the font size".

chaals


On Fri, 8 Mar 2002, Michelle Podd wrote:

  David,

  I've done a quick search through google and couldn't find what em stands
  for. I believe "e" stands for element but that's as close as I came. Here's
  the best description I could find from blooberry.com:

  Ems. A scaling factor relative to the value of the current element's
  'font-size' property. If 'em's are used in the 'font-size' property for an
  element, the scaling factor is relative to the value of the 'font-size'
  property of the parent element. If this type of unit is specified for the
  root element of a document, the scaling factor should be relative to the
  browser default value for the property.

  michelle

  ----- Original Message -----
  From: "David Poehlman" <poehlman1@comcast.net>
  To: "Michelle Podd" <mpodd@iqnetcom.com>
  Sent: Friday, March 08, 2002 2:14 PM
  Subject: Re: screen magnifiers and fragmented text


  > so what does e m stand for?
  >
  > ----- Original Message -----
  > From: "Michelle Podd" <mpodd@iqnetcom.com>
  > To: "David Poehlman" <poehlman1@comcast.net>
  > Sent: Friday, March 08, 2002 9:21 AM
  > Subject: Re: screen magnifiers and fragmented text
  >
  >
  > An em is a way to express a size value (for font, line-height or other
  > things) in a relative way as opposed to a fixed way. It allows the user
  > to
  > increase or decrease the fon't size through his browser.
  >
  >
  > ----- Original Message -----
  > From: "David Poehlman" <poehlman1@comcast.net>
  > To: "Michelle Podd" <mpodd@iqnetcom.com>
  > Sent: Thursday, March 07, 2002 1:47 PM
  > Subject: Re: screen magnifiers and fragmented text
  >
  >
  > > what is an em?  sorry to ask and I probably know but cannot put my
  > mind
  > > to it.
  > >
  > > ----- Original Message -----
  > > From: "Michelle Podd" <mpodd@iqnetcom.com>
  > > To: "WAI (E-mail)" <w3c-wai-ig@w3.org>
  > > Sent: Thursday, March 07, 2002 12:31 PM
  > > Subject: screen magnifiers and fragmented text
  > >
  > >
  > > Anyone ever have text "fragment" when using a screen magnifier? Any
  > > ideas
  > > why that would happen?
  > >
  > > At www.accessdome.com/preview I'm using Verdana as a main body font.
  > The
  > > size is expressed in em's. I'm getting a feedback from a lady using
  > > Zoomtext
  > > Extra Level 2 on a new PC through IE6. She tells me that the software
  > > acts
  > > as a screen magnifier and a screen reader. On the magnification side,
  > > she
  > > says that the headings (which are Georgia font) enlarge just fine
  > while
  > > some
  > > (but not all) of the body text fragments and is hard to read when
  > > magnified.
  > > I asked her to look at the National Organization on Disability site
  > >
  > >
  > http://www.nod.org/cont/dsp_cont_loc_hme.cfm?locationId=12&locationNm=Ho
  > > me )
  > > which I'm told is highly accessible. Her feedback was that the regular
  > > text
  > > enlarged properly but any link text was fragmented.
  > >
  > > My only guess is regarding the use of styles - the inheritance rule.
  > > Netscape 4.x has inheritance issues (among many many many other
  > problems
  > > but
  > > I won't go there). I've got a separate style sheet for Netscape
  > however
  > > in
  > > places where it doesn't listen to the font-size, I add a class to
  > force
  > > it.
  > > For example, I have a style applied to <p> and <td>. In my web page, I
  > > have
  > > a table. IE 5.x renders the font just fine but in Netscape, it ignored
  > > the
  > > size (it displayed the proper font-family however so go figure). So I
  > > add
  > > class="table" (which contain the same properties as my regular body
  > > font)
  > > to the table tag then most times, the font size displays properly in
  > > both
  > > IE5.x and Netscapte 4.x.  Here's part of my netscape style sheet. The
  > > one
  > > for "everyone else" is exactly the same, only the values are
  > different.
  > >
  > > p, body
  > > {
  > > font-family: verdana,arial,helvetica,sans-serif;
  > > font-size: .8em;
  > > color: #333333;
  > > }
  > >
  > > p
  > > {line-height: 1.1em;}
  > >
  > > .table
  > > {
  > > font-size: .8em;
  > > line-height: 1.1em;
  > > }
  > >
  > > td
  > > {
  > > font-family: verdana,arial,helvetica,sans-serif;
  > > font-size: .8em;
  > > color: #333333;
  > > }
  > >
  > > So, do you think the fragmentation occurs because of a style being
  > > applied
  > > twice?
  > >
  > > Any assistance is appreciated,
  > > Michelle Podd
  > > Web Designer
  > >
  > >
  > >
  > >
  >
  >
  >
  >



-- 
Charles McCathieNevile    http://www.w3.org/People/Charles  phone: +61 409 134 136
W3C Web Accessibility Initiative     http://www.w3.org/WAI    fax: +1 617 258 5999
Location: 21 Mitchell street FOOTSCRAY Vic 3011, Australia
(or W3C INRIA, Route des Lucioles, BP 93, 06902 Sophia Antipolis Cedex, France)
Received on Friday, 8 March 2002 15:09:30 GMT

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