IE6 will shrink-wrap elements with layout instead of allowing content to flow outside of the border-box. Add a test for this and do not remove the overflow property after an animation in IE6.

src/effects.js

@@ -36,17 +36,23 @@ jQuery.fn.extend({
 			return this.animate( genFx("show", 3), speed, easing, callback);
 		} else {
 			for ( var i = 0, j = this.length; i < j; i++ ) {
+				// Reset the inline display of this element to learn if it is
+				// being hidden by cascaded rules or not
+				if ( !jQuery.data(this[i], "olddisplay") && this[i].style.display === "none" ) {
+					this[i].style.display = "";
+				}
+
 				// Set elements which have been overridden with display: none
 				// in a stylesheet to whatever the default browser style is
 				// for such an element
-				if ( jQuery.css( this[i], "display" ) === "none" && this[i].style.display !== "none" ) {
+				if ( jQuery.css( this[i], "display" ) === "none" && this[i].style.display === "" ) {
 					jQuery.data(this[i], "olddisplay", defaultDisplay(this[i].nodeName));
 				}
 			}
 
-			// Set the display of the elements in a second loop
+			// Set the display of most of the elements in a second loop
 			// to avoid the constant reflow
-			for ( i = 0, j = this.length; i < j; i++ ) {
+			for ( i = 0; i < j; i++ ) {
 				this[i].style.display = jQuery.data(this[i], "olddisplay") || "";
 			}
 
@@ -59,17 +65,17 @@ jQuery.fn.extend({
 			return this.animate( genFx("hide", 3), speed, easing, callback);
 
 		} else {
-			for ( var i = 0, l = this.length; i < l; i++ ) {
+			for ( var i = 0, j = this.length; i < j; i++ ) {
 				var old = jQuery.data(this[i], "olddisplay");
-				if ( !old && old !== "none" ) {
+				if ( !old ) {
 					jQuery.data( this[i], "olddisplay", jQuery.css( this[i], "display" ) );
 				}
 			}
 
 			// Set the display of the elements in a second loop
 			// to avoid the constant reflow
-			for ( var j = 0, k = this.length; j < k; j++ ) {
-				this[j].style.display = "none";
+			for ( i = 0; i < j; i++ ) {
+				this[i].style.display = "none";
 			}
 
 			return this;
@@ -115,7 +121,8 @@ jQuery.fn.extend({
 			// test suite
 
 			var opt = jQuery.extend({}, optall), p,
-				hidden = this.nodeType === 1 && jQuery(this).is(":hidden"),
+				isElement = this.nodeType === 1,
+				hidden = isElement && jQuery(this).is(":hidden"),
 				self = this;
 
 			for ( p in prop ) {
@@ -131,7 +138,7 @@ jQuery.fn.extend({
 					return opt.complete.call(this);
 				}
 
-				if ( ( p === "height" || p === "width" ) ) {
+				if ( isElement && ( p === "height" || p === "width" ) ) {
 					// Make sure that nothing sneaks out
 					// Record all 3 overflow attributes because IE does not
 					// change the overflow attribute when overflowX and
@@ -141,8 +148,8 @@ jQuery.fn.extend({
 					// Set display property to inline-block for height/width
 					// animations on inline elements that are having width/height
 					// animated
-					if ( jQuery.curCSS( this, "display" ) === "inline" &&
-					jQuery.curCSS( this, "float" ) === "none" ) {
+					if ( jQuery.css( this, "display" ) === "inline" &&
+						jQuery.css( this, "float" ) === "none" ) {
 						if ( !jQuery.support.inlineBlockNeedsLayout ) {
 							this.style.display = "inline-block";
 						} else {
@@ -168,7 +175,7 @@ jQuery.fn.extend({
 				}
 			}
 
-			if ( opt.overflow != null ) {
+			if ( opt.overflow != null || (jQuery.support.shrinkWrapBlocks && isElement) ) {
 				this.style.overflow = "hidden";
 			}
 
@@ -401,7 +408,7 @@ jQuery.fx.prototype = {
 
 			if ( done ) {
 				// Reset the overflow
-				if ( this.options.overflow != null ) {
+				if ( this.options.overflow != null && (!jQuery.support.shrinkWrapBlocks || !jQuery.css( this.elem, "hasLayout" )) ) {
 					this.elem.style.overflow = this.options.overflow[0];
 					this.elem.style.overflowX = this.options.overflow[1];
 					this.elem.style.overflowY = this.options.overflow[2];

src/support.js

@@ -67,6 +67,7 @@
 		noCloneEvent: true,
 		boxModel: null,
 		inlineBlockNeedsLayout: false,
+		shrinkWrapBlocks: false,
 		reliableHiddenOffsets: true
 	};
 
@@ -120,17 +121,25 @@
 		document.body.appendChild( div );
 		jQuery.boxModel = jQuery.support.boxModel = div.offsetWidth === 2;
 
-		// Check if natively block-level elements act like inline-block
-		// elements when setting their display to 'inline'
-		// (IE < 8 does this)
 		if ( 'zoom' in div.style ) {
+			// Check if natively block-level elements act like inline-block
+			// elements when setting their display to 'inline' and giving
+			// them layout
+			// (IE < 8 does this)
 			div.style.display = 'inline';
-
-			// Layout is necessary to trigger this “feature”
 			div.style.zoom = 1;
 			jQuery.support.inlineBlockNeedsLayout = div.offsetWidth === 2;
+
+			// Check if elements with layout shrink-wrap their children
+			// (IE 6 does this)
+			div.style.display = '';
+			div.innerHTML = '<div style="width:4px;"></div>';
+			jQuery.support.shrinkWrapBlocks = div.offsetWidth !== 2;
 		}
 
+		div.innerHTML = '<table><tr><td style="padding:0;display:none"></td><td>t</td></tr></table>';
+		var tds = div.getElementsByTagName('td');
+
 		// Check if table cells still have offsetWidth/Height when they are set
 		// to display:none and there are still other visible table cells in a
 		// table row; if so, offsetWidth/Height are not reliable for use when
@@ -138,30 +147,36 @@
 		// display:none (it is still safe to use offsets if a parent element is
 		// hidden; don safety goggles and see bug #4512 for more information).
 		// (only IE 8 fails this test)
-		div.innerHTML = '<table><tr><td style="display:none"></td><td>t</td></tr></table>';
-		jQuery.support.reliableHiddenOffsets = div.getElementsByTagName('td')[0].offsetHeight === 0;
+		jQuery.support.reliableHiddenOffsets = tds[0].offsetHeight === 0;
+
+		tds[0].style.display = '';
+		tds[1].style.display = 'none';
+
+		// Check if empty table cells still have offsetWidth/Height
+		// (IE < 8 fail this test)
+		jQuery.support.reliableHiddenOffsets = jQuery.support.reliableHiddenOffsets && tds[0].offsetHeight === 0;
 		div.innerHTML = '';
 
 		document.body.removeChild( div ).style.display = 'none';
-		div = null;
+		div = tds = null;
 	});
 
 	// Technique from Juriy Zaytsev
 	// http://thinkweb2.com/projects/prototype/detecting-event-support-without-browser-sniffing/
-	var eventSupported = function( eventName ) { 
-		var el = document.createElement("div"); 
-		eventName = "on" + eventName; 
+	var eventSupported = function( eventName ) {
+		var el = document.createElement("div");
+		eventName = "on" + eventName;
 
-		var isSupported = (eventName in el); 
-		if ( !isSupported ) { 
-			el.setAttribute(eventName, "return;"); 
-			isSupported = typeof el[eventName] === "function"; 
-		} 
-		el = null; 
+		var isSupported = (eventName in el);
+		if ( !isSupported ) {
+			el.setAttribute(eventName, "return;");
+			isSupported = typeof el[eventName] === "function";
+		}
+		el = null;
 
-		return isSupported; 
+		return isSupported;
 	};
-	
+
 	jQuery.support.submitBubbles = eventSupported("submit");
 	jQuery.support.changeBubbles = eventSupported("change");