What Does a Star-Preceded Property Mean in Css

What does a star-preceded property mean in CSS?

This is the "star property hack" along the same lines as the "underscore hack." It includes junk before the property that IE ignores (the * works up to IE 7, the _ up to IE 6).

What does an asterisk (*) do in a CSS selector?

It is a wildcard, this means it will select all elements within that portion of the DOM.

For example, if I want apply margin to every element on my entire page you can use:

* {
    margin: 10px;
}

You can also use this within sub-selections, for example the following would add a margin to all elements within a paragraph tag:

p * {
    margin: 10px;
}

Your example is doing some css trickery to apply consecutive borders and margins to elements to give them multiple coloured borders. For example, a white border surrounded by a black border.

Purpose of asterisk before a CSS property

It is a browser specific CSS hack for versions 7 or below of Internet Explorer.

*property: value

Although Internet Explorer 7 corrected
its behavior when a property name is
prefixed with an underscore or a
hyphen, other non-alphanumeric
character prefixes are treated as they
were in IE6. Therefore, if you add a
non-alphanumeric character such as an
asterisk (*) immediately before a
property name, the property will be
applied in IE and not in other
browsers. Unlike with the hyphen and
underscore method, the CSS
specification makes no reservations
for the asterisk as a prefix, so use
of this hack could result in
unexpected behavior as the CSS
specifications evolve.

*property: value applies the property value in IE 7 and below. It may or may
not work in future versions. Warning:
this uses invalid CSS.

From: http://www.javascriptkit.com/dhtmltutors/csshacks3.shtml

What does *zoom:1 do in bootstrap?

It's like an inline conditional statement for IE5.5 - IE7. Only IE 5.5, IE6, and IE7 will display zoom: 1 because of the inline * (known as the "star property hack"). Similar to the IE6 hack with the underscore _.

See: http://snook.ca/archives/html_and_css/targetting_ie7

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