handle errors and fix join form

app/assets/stylesheets/application.scss

@@ -85,6 +85,13 @@ a {
   width: 60%;
 }
 
+.center-page {
+  position: absolute;
+  top: 50%;
+  left:50%;
+  transform: translate(-50%,-50%);
+}
+
 iframe{
   position: absolute;
   top: 0;

app/assets/stylesheets/errors.scss

@@ -0,0 +1,3 @@
+// Place all the styles related to the Errors controller here.
+// They will automatically be included in application.css.
+// You can use Sass (SCSS) here: http://sass-lang.com/