fix css

src/client/styles/scss/_mixins.scss

@@ -49,14 +49,14 @@
         & > .row,
         .page-editor-preview-container,
         .page-editor-preview-body {
-          height: calc(100vh - #{$header-plus-footer} +17px);
-          min-height: calc(100vh - #{$header-plus-footer} + 17px); // for IE11
+          height: calc(100vh - #{$header-plus-footer} +19px);
+          min-height: calc(100vh - #{$header-plus-footer} + 19px); // for IE11
         }
 
         // left(editor)
         .page-editor-editor-container {
-          height: calc(100vh - #{$header-plus-footer} +17px);
-          min-height: calc(100vh - #{$header-plus-footer} +17px); // for IE11
+          height: calc(100vh - #{$header-plus-footer} +19px);
+          min-height: calc(100vh - #{$header-plus-footer} +19px); // for IE11
 
           .react-codemirror2,
           .CodeMirror,
@@ -73,8 +73,8 @@
         .hackmd-error,
         #iframe-hackmd-container > iframe {
           width: 100%;
-          height: calc(100vh - #{$header-plus-footer} + 30px);
-          min-height: calc(100vh - #{$header-plus-footer} + 30px); // for IE11
+          height: calc(100vh - #{$header-plus-footer} + 33px);
+          min-height: calc(100vh - #{$header-plus-footer} + 33px); // for IE11
         }
       }
     }