diff --git a/client/dist/styles/bundle.css b/client/dist/styles/bundle.css
index 4803e9bb..a9030a4f 100644
--- a/client/dist/styles/bundle.css
+++ b/client/dist/styles/bundle.css
@@ -1 +1 @@
-#cms-page-history-versions tr.loading{color:#999}#cms-page-history-versions tr.loading td:hover{cursor:none}#cms-page-history-versions td:hover{cursor:pointer}.CMSPageHistoryController{overflow:hidden}.CMSPageHistoryController ins{background-color:#dfd;padding:2px;text-decoration:none}.CMSPageHistoryController del{background-color:#fdd;padding:2px;color:#f44}.CMSPageHistoryController .htmleditorfield.readonly img{max-width:100%;height:auto}.CMSPageHistoryController .cms-content-tools.collapsed{overflow:hidden}#cms-content-listview .cms-tree-expand-trigger,#cms-content-treeview .cms-tree-expand-trigger{display:none}.cms-content-tools #cms-content-treeview .cms-content-toolbar{border-bottom:none;-webkit-box-shadow:none;box-shadow:none;margin-bottom:0}.cms-content-tools #cms-content-treeview .cms-tree-expand-trigger{display:block;float:left;margin:0 0 2px}.cms-content-tools #cms-content-treeview .cms-tree-expand-trigger span.ui-button-text{padding-right:8px}.cms-content-tools #cms-content-treeview .cms-tree .badge{display:none}.cms-content-tools #cms-content-treeview .cms-tree .jstree-clicked>.text>.badge,.cms-content-tools #cms-content-treeview .cms-tree a:hover>.text>.badge{display:inline-block}#cms-content-tools-CMSMain .search-form{right:0}.cms-list .cms-list__item-breadcrumbs{margin-left:21px;margin-bottom:0;font-size:.9em;word-break:break-word}.cms-content-toolbar .view-controls{margin-top:0}.cms-content-toolbar .view-controls .page-view-link{display:inline-block;margin-right:-5px}.cms-content-toolbar .view-controls.view-controls--listview .font-icon-list,.cms-content-toolbar .view-controls.view-controls--treeview .font-icon-tree{display:none}.field.urlsegment .input-group{width:auto;-webkit-flex-wrap:nowrap;flex-wrap:nowrap}.field.urlsegment.loading .form__field-label{background-image:url(data:image/gif;base64,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);background-repeat:no-repeat;background-position:100%;padding-right:20px}.field.urlsegment .URL-link{padding-top:8px;display:inline-block}.field.urlsegment input.text{-webkit-box-flex:0;-webkit-flex:0 1 250px;flex:0 1 250px}.field.urlsegment .input-group-append{z-index:2}.field.urlsegment .input-group-append:last-of-type{z-index:1}.field.urlsegment .input-group-append .btn{margin-top:0;padding-top:.5385rem;padding-bottom:.5385rem}.field.urlsegment .help{margin-left:0}.field.urlsegment .edit-holder{display:none}.field.urlsegment .edit-holder .form__field-description{clear:both}.form__field-update-url{border-radius:0 3px 3px 0;margin-right:0;margin-left:-1px}
\ No newline at end of file
+#cms-page-history-versions tr.loading{color:#999}#cms-page-history-versions tr.loading td:hover{cursor:none}#cms-page-history-versions td:hover{cursor:pointer}.CMSPageHistoryController{overflow:hidden}.CMSPageHistoryController ins{background-color:#dfd;padding:2px;text-decoration:none}.CMSPageHistoryController del{background-color:#fdd;padding:2px;color:#f44}.CMSPageHistoryController .htmleditorfield.readonly img{max-width:100%;height:auto}.CMSPageHistoryController .cms-content-tools.collapsed{overflow:hidden}#cms-content-listview .cms-tree-expand-trigger,#cms-content-treeview .cms-tree-expand-trigger{display:none}.cms-content-tools #cms-content-treeview .cms-content-toolbar{border-bottom:none;-webkit-box-shadow:none;box-shadow:none;margin-bottom:0}.cms-content-tools #cms-content-treeview .cms-tree-expand-trigger{display:block;float:left;margin:0 0 2px}.cms-content-tools #cms-content-treeview .cms-tree-expand-trigger span.ui-button-text{padding-right:8px}.cms-content-tools #cms-content-treeview .cms-tree .badge{display:none}.cms-content-tools #cms-content-treeview .cms-tree .jstree-clicked>.text>.badge,.cms-content-tools #cms-content-treeview .cms-tree a:hover>.text>.badge{display:inline-block}#cms-content-tools-CMSMain .search-form{right:0}.cms-list .cms-list__item-breadcrumbs{margin-left:21px;margin-bottom:0;font-size:.9em;word-break:break-word}.cms-content-toolbar .view-controls{margin-top:0}.cms-content-toolbar .view-controls .page-view-link{display:inline-block;margin-right:-5px}.cms-content-toolbar .view-controls.view-controls--listview .font-icon-list,.cms-content-toolbar .view-controls.view-controls--treeview .font-icon-tree{display:none}#pages-controller-cms-content,#pages-controller-cms-content+.cms-preview{width:50%}.field.urlsegment .input-group{width:auto;-webkit-flex-wrap:nowrap;flex-wrap:nowrap}.field.urlsegment.loading .form__field-label{background-image:url(data:image/gif;base64,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);background-repeat:no-repeat;background-position:100%;padding-right:20px}.field.urlsegment .URL-link{padding-top:8px;display:inline-block}.field.urlsegment input.text{-webkit-box-flex:0;-webkit-flex:0 1 250px;flex:0 1 250px}.field.urlsegment .input-group-append{z-index:2}.field.urlsegment .input-group-append:last-of-type{z-index:1}.field.urlsegment .input-group-append .btn{margin-top:0;padding-top:.5385rem;padding-bottom:.5385rem}.field.urlsegment .help{margin-left:0}.field.urlsegment .edit-holder{display:none}.field.urlsegment .edit-holder .form__field-description{clear:both}.form__field-update-url{border-radius:0 3px 3px 0;margin-right:0;margin-left:-1px}
\ No newline at end of file
diff --git a/client/src/styles/legacy/_CMSMain.scss b/client/src/styles/legacy/_CMSMain.scss
index 53281e46..40748009 100644
--- a/client/src/styles/legacy/_CMSMain.scss
+++ b/client/src/styles/legacy/_CMSMain.scss
@@ -142,6 +142,14 @@
 
 }
 
+/* -------------------------------------------------------------------
+ * Container for editor + preview
+ * ----------------------------------------------------------------- */
+#pages-controller-cms-content,
+#pages-controller-cms-content + .cms-preview {
+  width: 50%; // Effectively inert, allows IE 11 to do its sizing math properly
+}
+
 /** ------------------------------------------------------------------
  * URLSegment field
  * ----------------------------------------------------------------- */
diff --git a/templates/SilverStripe/CMS/Controllers/Includes/CMSMain_Content.ss b/templates/SilverStripe/CMS/Controllers/Includes/CMSMain_Content.ss
index 63b3fae1..0dbb1653 100644
--- a/templates/SilverStripe/CMS/Controllers/Includes/CMSMain_Content.ss
+++ b/templates/SilverStripe/CMS/Controllers/Includes/CMSMain_Content.ss
@@ -3,7 +3,7 @@
 
 	<div class="fill-height flexbox-area-grow">
 		<div class="cms-content-header north">
-			<div class="cms-content-header-info flexbox-area-grow vertical-align-items fill-width">
+			<div class="cms-content-header-info flexbox-area-grow vertical-align-items">
 				<a href="$BreadcrumbsBackLink" class="btn btn-secondary btn--no-text font-icon-left-open-big hidden-lg-up toolbar__back-button"></a>
 				<% include SilverStripe\\Admin\\CMSBreadcrumbs %>
 			</div>