CSS Filter - Star Hack

Star Hack

Versions 7 and below of Internet Explorer recognize properties which are preceded by non-alphanumeric characters except an underscore or a hyphen (after discarding the prefix). All other browsers ignore such properties as invalid. Therefore, a property that is preceded by an non-alphanumeric character other than an underscore or a hyphen, such as an asterisk, is applied exclusively in Internet Explorer 7 and below.

This hack uses invalid CSS and there are valid CSS directives to accomplish a similar result. On the other hand, this hack doesn't change the specificity of a selector making maintenance and extension of a CSS file easier.