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On 2009-07-22, Johannes Koch <koch (AT) w3development (DOT) de> wrote:

Ben C schrieb:
On 2009-07-21, shapper <mdmoura (AT) gmail (DOT) com> wrote:

1. The color warnings.
Does this mean I always need to set a background color even if
transparent?

There is a small risk of a user stylesheet intervening and changing your
transparent to white. But I wouldn't really worry about that.

It would be quite strange for a user to have a stylesheet that set white
backgrounds on things and not color, unless they were trying to make
text invisible.

Consider the following.

author stylesheet:

body {
color: #000;
background: #fff
}
div#content {
color: #000;
background: transparent
}


user stylesheet:

body {
color: #fff;
background: #000
}


result:

body { /* user stylesheet wins */
color: #fff;
background: #000
}
div#content { /* from author stylesheet */
color: #000;
background: transparent /* #000 (from user stylesheet) */
}

Yes, that could happen, but perhaps the real lesson here is: don't use
background: transparent unless you're fairly sure you've also set the
background of whatever's behind (and of whatever's behind that if it's
transparent).

There will always be some risk even then, because whatever rule you used
to set the background of _that_ element (the one behind) may be
overridden by something more specific while the rule you used to set
text colour on the foreground may not be.

But there is always some degree of risk whatever you do-- the user can
always override either the background or the text colour but not
necessarily both, even if you always set background and color in the
same rule.

Ben C schrieb:

Yes, that could happen, but perhaps the real lesson here is: don't use
background: transparent unless you're fairly sure you've also set the
background of whatever's behind (and of whatever's behind that if it's
transparent).

Yes, transparent is dangerous.

But there is always some degree of risk whatever you do-- the user can
always override either the background or the text colour but not
necessarily both, even if you always set background and color in the
same rule.

If the user does this, then it is his/her fault. You as a CSS author
should do your job properly, so that a proper user style sheet will not
cause problems with yout author style sheet.

--
Johannes Koch
In te domine speravi; non confundar in aeternum.
(Te Deum, 4th cent.)