The simplest way to define a CSS rule in jQuery might be:
$(".sth").css("color", "#f00");
To define more than one CSS rule in a single jQuery line:
$(".sth").css("color", "#f00").css("font-style", "italic").css("text-decoration", "underline");
Which simply doesn’t look that good, especially if you intend to add more. A better way to specify multiple CSS rules or properties with jQuery is by a JSON object:
$(".sth").css( {'color' : '#f00', 'font-style' : 'italic', 'text-decoration' : 'underline'} );
However, it is recommended that you use .addClass() instead of .css() to separate the JavaScript logics and CSS styles for maintainability.