If the property name includes a "-", put it between quotation marks:

Edit code and click me	Your Result (Some examples do not work in Google Chrome):
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <script src="http://code.jquery.com/jquery-latest.js"></script> <script> $(document).ready(function(){ $("p").hover(function () { $(this).css({ "background-color":"yellow", "font-weight":"bolder" }); }, function () { var cssObj = { "background-color": "#ddd", "font-weight": "", color: "rgb(0,40,244)" } $(this).css(cssObj); }); }); </script> <style> p { color:green; } </style> </head> <body> <p> Move the mouse over a paragraph. </p> <p> Like this one or the one above. </p> </body> </html>
Edit the code above and click to see the result	www.xhtml.co.il - Try it yourself