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RE: Relative vs. absolute units

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From: John Foliot - bytown internet
Date: Mar 4, 2003 2:39PM

Julian,

sorry for not responding earlier... this one slipped through the cracks and
was only discovered during regular maintenance...

*Under normal circumstances* an em is 16px. I say normal, as this is based
on the fact that the end user generally does not change their default font
size. In IE, the only way to do that is to change the default font size
through the OS properties dialogue (Desktop>> right click>>> properties).
In Netscape this measurement can be changed via the Edit>> Preferences
dialogue within the browser. If you have either version 6 or 7 installed
and check, you will see that the default font is actually set to a pixel
size, and not the older point size (which was what NN 4 used). Note, this
doesn't work in NN4, as that browser doesn't know what an "em" is. However,
like all unknowns, if the browser does not know what "it" is it ignores
"it"; technically, those images in NN4 would not have declared Height and
Width attributes, or at least none that had any real meaning to the browser.

Now should a user go in and change their default font size to something
larger, then the image will scale larger - proportionate to the font size
still, but again, you will experience a slight degradation of image quality.
For this reason I tend to restrict it to "mission critical" imagery - icons,
text buttons, etc., whereas photos, "design" imagery, etc. I still size in
pixels. It's not a perfect solution, but a stab in the (I hope) right
direction.

cheers!

JF

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