Determine whether a layer is hidden:
$("#id").css ("display")=="none" ;
On all matching elements, set the value of a style attribute:
$("p").css("color","red");
An object of name/value pairs set as the style properties of all matching elements.
This is the best way to set a large number of style attributes on all matching elements
$("p").css({ color: "#ff0011", background: "blue" });
If If the attribute name contains "-", quotation marks must be used:
$("p").css({ "margin-left": "10px", "background-color": "blue" });