diff --git a/assets/css/src/newsletter_editor/components/sidebar.styl b/assets/css/src/newsletter_editor/components/sidebar.styl
index 57fdd45542..3aa02f1fee 100644
--- a/assets/css/src/newsletter_editor/components/sidebar.styl
+++ b/assets/css/src/newsletter_editor/components/sidebar.styl
@@ -150,10 +150,15 @@ $widget-icon-width = 30px
 
 .mailpoet_browser_preview_container
   flex: 1 1 auto
-  position: relative
-  margin: 15px auto auto auto
+  margin: 15px auto 0 auto
   transition: width 0.5s
   box-sizing: border-box
+  height: 100%
+  padding: 20px
+  border: 1px solid #979797
+  border-radius: 20px
+  display: flex
+  flex-direction: column
 
 .mailpoet_browser_preview_container_desktop
   width: 100%
@@ -164,3 +169,4 @@ $widget-icon-width = 30px
 .mailpoet_browser_preview_iframe
   box-sizing: border-box
   border: 1px solid #c3c3c3
+  flex: 1 1 auto