Made sure that css() in IE handles negative non-px values correctly. Fixes #3331.

src/css.js

@@ -5,8 +5,8 @@ var rexclude = /z-?index|font-?weight|opacity|zoom|line-?height/i,
 	rfloat = /float/i,
 	rdashAlpha = /-([a-z])/ig,
 	rupper = /([A-Z])/g,
-	rnumpx = /^\d+(?:px)?$/i,
-	rnum = /^\d/,
+	rnumpx = /^-?\d+(?:px)?$/i,
+	rnum = /^-?\d/,
 
 	// cache check for defaultView.getComputedStyle
 	getComputedStyle = document.defaultView && document.defaultView.getComputedStyle,

test/unit/css.js

@@ -59,13 +59,16 @@ test("css(String|Hash)", function() {
 });
 
 test("css(String, Object)", function() {
-	expect(20);
+	expect(21);
 	ok( jQuery('#nothiddendiv').is(':visible'), 'Modifying CSS display: Assert element is visible');
 	jQuery('#nothiddendiv').css("display", 'none');
 	ok( !jQuery('#nothiddendiv').is(':visible'), 'Modified CSS display: Assert element is hidden');
 	jQuery('#nothiddendiv').css("display", 'block');
 	ok( jQuery('#nothiddendiv').is(':visible'), 'Modified CSS display: Assert element is visible');
 
+	jQuery("#nothiddendiv").css("top", "-1em");
+	ok( jQuery("#nothiddendiv").css("top"), -16, "Check negative number in EMs." );
+
 	jQuery('#floatTest').css('styleFloat', 'left');
 	equals( jQuery('#floatTest').css('styleFloat'), 'left', 'Modified CSS float using "styleFloat": Assert float is left');
 	jQuery('#floatTest').css('cssFloat', 'right');