diff --git a/src/ajax/load.js b/src/ajax/load.js
@@ -25,7 +25,7 @@ jQuery.fn.load = function( url, params, callback ) {
 		off = url.indexOf(" ");
 
 	if ( off >= 0 ) {
-		selector = url.slice( off );
+		selector = jQuery.trim( url.slice( off ) );
 		url = url.slice( 0, off );
 	}
 

diff --git a/src/core.js b/src/core.js
@@ -216,7 +216,7 @@ jQuery.extend({
 		// parseFloat NaNs numeric-cast false positives (null|true|false|"")
 		// ...but misinterprets leading-number strings, particularly hex literals ("0x...")
 		// subtraction forces infinities to NaN
-		return obj - parseFloat( obj ) >= 0;
+		return !jQuery.isArray( obj ) && obj - parseFloat( obj ) >= 0;
 	},
 
 	isPlainObject: function( obj ) {

diff --git a/src/core/ready.js b/src/core/ready.js
@@ -51,8 +51,9 @@ jQuery.extend({
 		readyList.resolveWith( document, [ jQuery ] );
 
 		// Trigger any bound ready events
-		if ( jQuery.fn.trigger ) {
-			jQuery( document ).trigger("ready").off("ready");
+		if ( jQuery.fn.triggerHandler ) {
+			jQuery( document ).triggerHandler( "ready" );
+			jQuery( document ).off( "ready" );
 		}
 	}
 });

diff --git a/src/css.js b/src/css.js
@@ -29,8 +29,8 @@ var
 
 	cssShow = { position: "absolute", visibility: "hidden", display: "block" },
 	cssNormalTransform = {
-		letterSpacing: 0,
-		fontWeight: 400
+		letterSpacing: "0",
+		fontWeight: "400"
 	},
 
 	cssPrefixes = [ "Webkit", "O", "Moz", "ms" ];

diff --git a/src/event.js b/src/event.js
@@ -583,7 +583,7 @@ jQuery.event = {
 
 				// Support: Firefox 20+
 				// Firefox doesn't alert if the returnValue field is not set.
-				if ( event.result !== undefined ) {
+				if ( event.result !== undefined && event.originalEvent ) {
 					event.originalEvent.returnValue = event.result;
 				}
 			}

diff --git a/test/data/core/onready.html b/test/data/core/onready.html
@@ -0,0 +1,24 @@
+<!doctype html>
+<html>
+<head>
+	<meta http-equiv="Content-type" content="text/html; charset=utf-8"/>
+	<title>alias-masked DOM properties (#14074)</title>
+	<script>
+		var error = false;
+		window.onready = function() { error = "Called window.onready"; };
+	</script>
+	<script src="../../jquery.js"></script>
+</head>
+<body>
+	<form>
+		<input type="text" id="nodeName"/>
+	</form>
+	<script>
+		jQuery(function() {
+			setTimeout( function() {
+				window.parent.iframeCallback( error );
+			});
+		});
+	</script>
+</body>
+</html>
diff --git a/test/data/event/triggerunload.html b/test/data/event/triggerunload.html
@@ -0,0 +1,18 @@
+<!doctype html>
+<html>
+	<script src="../../jquery.js"></script>
+	<script>
+		var called = false,
+			error = false;
+
+		window.onerror = function() { error = true; };
+
+		jQuery( window ).on( "beforeunload", function( event ) {
+			called = true;
+			return "maybe";
+		}).on( "load", function( event ) {
+			$( window ).triggerHandler( "beforeunload" );
+			window.parent.iframeCallback( called && !error );
+		});
+	</script>
+</html>
diff --git a/test/data/test3.html b/test/data/test3.html
@@ -1,3 +1,4 @@
 <div class="user">This is a user</div>
 <div class="user">This is a user</div>
 <div class="teacher">This is a teacher</div>
+<div id="superuser">This is a superuser</div>
diff --git a/test/unit/ajax.js b/test/unit/ajax.js
@@ -1807,6 +1807,14 @@ module( "ajax", {
 		});
 	});
 
+	// Selector should be trimmed to avoid leading spaces (#14773)
+	asyncTest( "jQuery.fn.load( URL_SELECTOR with spaces )", 1, function() {
+		jQuery("#first").load( "data/test3.html   #superuser ", function() {
+			strictEqual( jQuery( this ).children("div").length, 1, "Verify that specific elements were injected" );
+			start();
+		});
+	});
+
 	asyncTest( "jQuery.fn.load( String, Function ) - simple: inject text into DOM", 2, function() {
 		jQuery("#first").load( url("data/name.html"), function() {
 			ok( /^ERROR/.test(jQuery("#first").text()), "Check if content was injected into the DOM" );

diff --git a/test/unit/core.js b/test/unit/core.js
@@ -457,7 +457,7 @@ test("isFunction", function() {
 });
 
 test( "isNumeric", function() {
-	expect( 36 );
+	expect( 38 );
 
 	var t = jQuery.isNumeric,
 		Traditionalists = /** @constructor */ function(n) {
@@ -505,6 +505,8 @@ test( "isNumeric", function() {
 	equal( t(Number.NEGATIVE_INFINITY), false, "Negative Infinity");
 	equal( t(rong), false, "Custom .toString returning non-number");
 	equal( t({}), false, "Empty object");
+	equal( t( [] ), false, "Empty array" );
+	equal( t( [ 42 ] ), false, "Array with one number" );
 	equal( t(function(){} ), false, "Instance of a function");
 	equal( t( new Date() ), false, "Instance of a Date");
 	equal( t(function(){} ), false, "Instance of a function");
@@ -1514,3 +1516,10 @@ testIframeWithCallback( "Tolerating alias-masked DOM properties (#14074)", "core
 			deepEqual( errors, [], "jQuery loaded" );
 	}
 );
+
+testIframeWithCallback( "Don't call window.onready (#14802)", "core/onready.html",
+	function( error ) {
+			expect( 1 );
+			equal( error, false, "no call to user-defined onready" );
+	}
+);
diff --git a/test/unit/css.js b/test/unit/css.js
@@ -813,12 +813,13 @@ testIframeWithCallback( "css('width') should work correctly before document read
 );
 
 test("certain css values of 'normal' should be convertable to a number, see #8627", function() {
-	expect ( 2 );
+	expect ( 3 );
 
 	var el = jQuery("<div style='letter-spacing:normal;font-weight:normal;'>test</div>").appendTo("#qunit-fixture");
 
 	ok( jQuery.isNumeric( parseFloat( el.css("letterSpacing") ) ), "css('letterSpacing') not convertable to number, see #8627" );
 	ok( jQuery.isNumeric( parseFloat( el.css("fontWeight") ) ), "css('fontWeight') not convertable to number, see #8627" );
+	equal( typeof el.css( "fontWeight" ), "string", ".css() returns a string" );
 });
 
 // only run this test in IE9

diff --git a/test/unit/event.js b/test/unit/event.js
@@ -2434,6 +2434,11 @@ testIframeWithCallback( "Focusing iframe element", "event/focusElem.html", funct
 	ok( isOk, "Focused an element in an iframe" );
 });
 
+testIframeWithCallback( "triggerHandler(onbeforeunload)", "event/triggerunload.html", function( isOk ) {
+	expect( 1 );
+	ok( isOk, "Triggered onbeforeunload without an error" );
+});
+
 // need PHP here to make the incepted IFRAME hang
 if ( hasPHP ) {
 	testIframeWithCallback( "jQuery.ready synchronous load with long loading subresources", "event/syncReady.html", function( isOk ) {