sfhover is a replacement for the hover psuedo-class, used for showing a "Suckerfish" dropdown menu in IE6. You need it because IE6 only supports the hover class for anchors, not list items. I think that is how it works, check this out for more info: http://www.htmldog.com/articles/suckerfish/dropdowns/
To be clear: there is no such thing as 'sfhover' in CSS. Apparently, this is a javscript function to fix IE so it will work with standard markup.
it is a class name, used in a javascript custom function for normal hover effect replacement. hover effect is style that applied when user's mouse cursor hover on an html element.
it is actually a java script function not a CSS property. and it is used to apply hover effect on drop down menu in IE6.