no problems = green box

public/css/main.css

@@ -94,7 +94,8 @@ nav .container {
 
 div.info,
 div.warn,
-div.error {
+div.error,
+div.success {
     position: relative;
     padding: .5rem .8rem;
     margin-bottom: .5rem;
@@ -116,7 +117,13 @@ div.error {
     border-color: #f5c6cb;
 }
 
-div.show {
+div.success {
+    background: #e1f6e1;
+    border-color: #a9deaa;
+}
+
+div.show,
+div.success {
     display: block !important;
 }
 

public/js/selftest.js

@@ -309,6 +309,11 @@ function markSkipped(elem) {
     elem.className = 'warn';
 }
 
+function markSuccess(elem) {
+    elem.innerHTML = 'Done! No problems detected.';
+    elem.className = 'success';
+}
+
 function getStatusColumn(index) {
     return document.querySelector('#tests tr:nth-child('+(index+1)+') td:nth-child(3)');
 }
@@ -354,7 +359,7 @@ sleep(500).then(function(res) {
     log("----------");
     log("No problems detected.");
     showLogButton();
-    document.getElementById('status').innerHTML = "Done! No problems detected."
+    markSuccess(document.getElementById('status'));
 }).catch(function(err) {
     log("----------");
     log("Test failed.");