Add error message and disabling of preview button

src/scss/tags.scss

@@ -31,6 +31,12 @@ button {
         color: $color-active-hover;
     }
 
+    &:disabled {
+        background: $color-white !important;
+        color: $color-gray-light !important;
+        cursor: default !important;
+    }
+
     &.large {
         margin: 2em 0;
         padding: 0.5em 0.5em;

src/scss/templates/markdown_image.scss

@@ -9,7 +9,7 @@ All rights reserved.
     position: relative; min-width: 33em;
 
     display: inline-block;
-    margin: 1em 2em 0 0;
+    margin: 0 2em 1em 0;
     overflow: hidden;
     vertical-align: top;
 
@@ -27,13 +27,16 @@ All rights reserved.
         }
     }
 
-    .fileName {
-        height: 3em;
+    .dynamic {
+        min-height: 7.5em; min-width: 22em;
+        margin: 0 0 3.5em 11em;
 
-        margin: 1em 0 7em 11em;
+        .fileName {
+            min-height: 2em;
 
-        p {
-            font-weight: bold;
+            p {
+                font-weight: bold;
+            }
         }
     }