Currently executing

 jQuery("#myid").css("top", top)
                .css("left", left)
                .etc...

with top = null is equivalent to executing css("top") without parameter. Thus an integer value is returned from css("top", top) call instead of "this". Thus executing of the consecutive operation css("left", left) results in an error.

I guess it would be more convenient to return this in case of css("xxx", null) calls.

I achieved this by adding

		if (arguments.length > 1 && value == undefined) return this;

line to the css() method. Though I'm not sure that this is the best solution as I'm not very well familiar with jQuery internals.

	css: function( key, value ) {
		// ignore negative width and height values
		if ( (key == 'width' || key == 'height') && parseFloat(value) < 0 )
			value = undefined;
		if (arguments.length > 1 && value == undefined) return this;
		return this.attr( key, value, "curCSS" );
	},

Regards, telega