Index: wp-admin/js/revisions.js
===================================================================
--- wp-admin/js/revisions.js	(revision 24705)
+++ wp-admin/js/revisions.js	(working copy)
@@ -452,6 +452,7 @@
 		render: function() {
 			wp.Backbone.View.prototype.render.apply( this, arguments );
 
+			$('html').css( 'overflow-y', 'scroll' );
 			$('#wpbody-content .wrap').append( this.el );
 			this.updateCompareTwoMode();
 			this.renderDiff( this.model.diff() );
@@ -532,7 +533,8 @@
 			tickCount = this.model.revisions.length - 1;
 			tickWidth = 1 / tickCount;
 
-			_(tickCount).times( function(){ this.$el.append( '<div></div>' ); }, this );
+			_(tickCount - 1).times( function(){ this.$el.append( '<div></div>' ); }, this );
+
 			this.$('div').css( 'width', ( 100 * tickWidth ) + '%' );
 		}
 	});
Index: wp-admin/css/wp-admin.css
===================================================================
--- wp-admin/css/wp-admin.css	(revision 24705)
+++ wp-admin/css/wp-admin.css	(working copy)
@@ -3500,10 +3500,6 @@
 /*------------------------------------------------------------------------------
   11.2 - Post Revisions
 ------------------------------------------------------------------------------*/
-body.revision-php {
-	overflow-y: scroll; /* Force a scrollbar, so centering doesn't jump */
-}
-
 .revisions-control-frame,
 .revisions-diff-frame {
 	position: relative;
@@ -3522,14 +3518,13 @@
 
 .revisions-tickmarks {
 	position: relative;
-	margin: 0 auto 0;
+	margin: 0 auto;
 	height: 0.8em;
 	z-index: 2;
 	top: 7px;
 	width: 70%;
 	-moz-box-sizing: border-box;
 	-webkit-box-sizing: border-box;
-	-ms-box-sizing: border-box; /* ie8 only */
 	box-sizing: border-box;
 }
 
@@ -3539,14 +3534,13 @@
 	float: left;
 	z-index: 10002;
 	border-style: solid;
-	border-width: 0 0 0 1px;
+	border-width: 0 1px 0 0;
 	-moz-box-sizing: border-box;
 	-webkit-box-sizing: border-box;
-	-ms-box-sizing: border-box; /* ie8 only */
 	box-sizing: border-box;
 }
 
-.revisions-tickmarks > div:first-of-type {
+.revisions-tickmarks > div:first-child {
 	border-left-width: 0;
 }
 
@@ -3559,6 +3553,7 @@
 	text-align: center;
 	vertical-align: middle;
 	opacity: 0;
+	filter: alpha(opacity=0);
 	margin: 0 auto;
 	width: 100%;
 	height: 32px;
@@ -3569,10 +3564,12 @@
 	-ms-transition:     opacity 0.5s;
 	-o-transition:      opacity 0.5s;
 	transition:         opacity 0.5s;
+	filter: alpha(opacity=0); /* ie8 and earlier */
 }
 
 .revisions.loading .loading-indicator {
 	opacity: 1;
+	filter: alpha(opacity=100); /* ie8 and earlier */
 }
 
 .revisions .diff {
@@ -3585,6 +3582,7 @@
 
 .revisions.loading .diff {
 	opacity: 0.5;
+	filter: alpha(opacity=50); /* ie8 and earlier */
 }
 
 .revisions-meta {
@@ -3612,7 +3610,7 @@
 
 .wp-slider {
 	width: 70%;
-	margin: 0 auto 0;
+	margin: 0 auto;
 	top: -3px;
 }