diff --git a/src/css.js b/src/css.js
index 210bed2e80..237caed4a4 100644
--- a/src/css.js
+++ b/src/css.js
@@ -1,7 +1,4 @@
-var curCSS, getStyles, iframe,
-	ralpha = /alpha\([^)]*\)/i,
-	ropacity = /opacity\s*=\s*([^)]*)/,
-	rposition = /^(top|right|bottom|left)$/,
+var curCSS, iframe,
 	// swappable if display is none or starts with table except "table", "table-cell", or "table-caption"
 	// see here for display values: https://developer.mozilla.org/en-US/docs/CSS/display
 	rdisplayswap = /^(none|table(?!-c[ea]).+)/,
@@ -50,6 +47,12 @@ function isHidden( elem, el ) {
 	return jQuery.css( elem, "display" ) === "none" || !jQuery.contains( elem.ownerDocument, elem );
 }
 
+// NOTE: we've included the "window" in window.getComputedStyle
+// because jsdom on node.js will break without it.
+function getStyles( elem ) {
+	return window.getComputedStyle( elem, null );
+}
+
 function showHide( elements, show ) {
 	var elem,
 		values = [],
@@ -294,99 +297,47 @@ jQuery.extend({
 	}
 });
 
-// NOTE: we've included the "window" in window.getComputedStyle
-// because jsdom on node.js will break without it.
-if ( window.getComputedStyle ) {
-	getStyles = function( elem ) {
-		return window.getComputedStyle( elem, null );
-	};
-
-	curCSS = function( elem, name, _computed ) {
-		var width, minWidth, maxWidth,
-			computed = _computed || getStyles( elem ),
-
-			// getPropertyValue is only needed for .css('filter') in IE9, see #12537
-			ret = computed ? computed.getPropertyValue( name ) || computed[ name ] : undefined,
-			style = elem.style;
-
-		if ( computed ) {
+curCSS = function( elem, name, _computed ) {
+	var width, minWidth, maxWidth,
+		computed = _computed || getStyles( elem ),
 
-			if ( ret === "" && !jQuery.contains( elem.ownerDocument, elem ) ) {
-				ret = jQuery.style( elem, name );
-			}
-
-			// A tribute to the "awesome hack by Dean Edwards"
-			// Chrome < 17 and Safari 5.0 uses "computed value" instead of "used value" for margin-right
-			// Safari 5.1.7 (at least) returns percentage for a larger set of values, but width seems to be reliably pixels
-			// this is against the CSSOM draft spec: http://dev.w3.org/csswg/cssom/#resolved-values
-			if ( rnumnonpx.test( ret ) && rmargin.test( name ) ) {
-
-				// Remember the original values
-				width = style.width;
-				minWidth = style.minWidth;
-				maxWidth = style.maxWidth;
-
-				// Put in the new values to get a computed value out
-				style.minWidth = style.maxWidth = style.width = ret;
-				ret = computed.width;
-
-				// Revert the changed values
-				style.width = width;
-				style.minWidth = minWidth;
-				style.maxWidth = maxWidth;
-			}
-		}
-
-		return ret;
-	};
-} else if ( document.documentElement.currentStyle ) {
-	getStyles = function( elem ) {
-		return elem.currentStyle;
-	};
+		// Support: IE9
+		// getPropertyValue is only needed for .css('filter') in IE9, see #12537
+		ret = computed ? computed.getPropertyValue( name ) || computed[ name ] : undefined,
+		style = elem.style;
 
-	curCSS = function( elem, name, _computed ) {
-		var left, rs, rsLeft,
-			computed = _computed || getStyles( elem ),
-			ret = computed ? computed[ name ] : undefined,
-			style = elem.style;
+	if ( computed ) {
 
-		// Avoid setting ret to empty string here
-		// so we don't default to auto
-		if ( ret == null && style && style[ name ] ) {
-			ret = style[ name ];
+		if ( ret === "" && !jQuery.contains( elem.ownerDocument, elem ) ) {
+			ret = jQuery.style( elem, name );
 		}
 
-		// From the awesome hack by Dean Edwards
-		// http://erik.eae.net/archives/2007/07/27/18.54.15/#comment-102291
-
-		// If we're not dealing with a regular pixel number
-		// but a number that has a weird ending, we need to convert it to pixels
-		// but not position css attributes, as those are proportional to the parent element instead
-		// and we can't measure the parent instead because it might trigger a "stacking dolls" problem
-		if ( rnumnonpx.test( ret ) && !rposition.test( name ) ) {
+		// Support: Chrome <17, Safari 5.1
+		// A tribute to the "awesome hack by Dean Edwards"
+		// Chrome < 17 and Safari 5.0 uses "computed value" instead of "used value" for margin-right
+		// Safari 5.1.7 (at least) returns percentage for a larger set of values, but width seems to be reliably pixels
+		// this is against the CSSOM draft spec: http://dev.w3.org/csswg/cssom/#resolved-values
+		if ( rnumnonpx.test( ret ) && rmargin.test( name ) ) {
 
 			// Remember the original values
-			left = style.left;
-			rs = elem.runtimeStyle;
-			rsLeft = rs && rs.left;
+			width = style.width;
+			minWidth = style.minWidth;
+			maxWidth = style.maxWidth;
 
 			// Put in the new values to get a computed value out
-			if ( rsLeft ) {
-				rs.left = elem.currentStyle.left;
-			}
-			style.left = name === "fontSize" ? "1em" : ret;
-			ret = style.pixelLeft + "px";
+			style.minWidth = style.maxWidth = style.width = ret;
+			ret = computed.width;
 
 			// Revert the changed values
-			style.left = left;
-			if ( rsLeft ) {
-				rs.left = rsLeft;
-			}
+			style.width = width;
+			style.minWidth = minWidth;
+			style.maxWidth = maxWidth;
 		}
+	}
+
+	return ret;
+};
 
-		return ret === "" ? "auto" : ret;
-	};
-}
 
 function setPositiveNumber( elem, value, subtract ) {
 	var matches = rnumsplit.exec( value );
@@ -547,50 +498,6 @@ jQuery.each([ "height", "width" ], function( i, name ) {
 	};
 });
 
-if ( !jQuery.support.opacity ) {
-	jQuery.cssHooks.opacity = {
-		get: function( elem, computed ) {
-			// IE uses filters for opacity
-			return ropacity.test( (computed && elem.currentStyle ? elem.currentStyle.filter : elem.style.filter) || "" ) ?
-				( 0.01 * parseFloat( RegExp.$1 ) ) + "" :
-				computed ? "1" : "";
-		},
-
-		set: function( elem, value ) {
-			var style = elem.style,
-				currentStyle = elem.currentStyle,
-				opacity = jQuery.isNumeric( value ) ? "alpha(opacity=" + value * 100 + ")" : "",
-				filter = currentStyle && currentStyle.filter || style.filter || "";
-
-			// IE has trouble with opacity if it does not have layout
-			// Force it by setting the zoom level
-			style.zoom = 1;
-
-			// if setting opacity to 1, and no other filters exist - attempt to remove filter attribute #6652
-			// if value === "", then remove inline opacity #12685
-			if ( ( value >= 1 || value === "" ) &&
-					jQuery.trim( filter.replace( ralpha, "" ) ) === "" &&
-					style.removeAttribute ) {
-
-				// Setting style.filter to null, "" & " " still leave "filter:" in the cssText
-				// if "filter:" is present at all, clearType is disabled, we want to avoid this
-				// style.removeAttribute is IE Only, but so apparently is this code path...
-				style.removeAttribute( "filter" );
-
-				// if there is no filter style applied in a css rule or unset inline opacity, we are done
-				if ( value === "" || currentStyle && !currentStyle.filter ) {
-					return;
-				}
-			}
-
-			// otherwise, set new filter values
-			style.filter = ralpha.test( filter ) ?
-				filter.replace( ralpha, opacity ) :
-				filter + " " + opacity;
-		}
-	};
-}
-
 // These hooks cannot be added until DOM ready because the support test
 // for it is not run until after DOM ready
 jQuery(function() {