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