Update file style.css

static/style.css

+body { padding-top: 56px; }
+.left-aligned { margin-left: auto; }
+.bg-dark { background-color: #343a40 !important; }
+.bg-hero { background-color: #45b06cff; }
+
+/* CALLOUT */
+.bd-callout { padding:1.25rem; margin-top:1.25rem; margin-bottom:1.25rem; border:1px solid #e9ecef; border-left-width:.25rem; border-radius:.25rem }
+.bd-callout h4 { margin-bottom:.25rem }
+.bd-callout p:last-child { margin-bottom:0 }
+.bd-callout code { border-radius:.25rem }
+.bd-callout+.bd-callout { margin-top:-.25rem }
+.bd-callout-info { border-left-color:#5bc0de }
+.bd-callout-warning { border-left-color:#f0ad4e }
+.bd-callout-danger { border-left-color:#d9534f }
+
+/* footer */
+footer a { color: white; font-weight: bold; text-decoration: none; }
+footer a:hover { color: white; text-decoration: underline; }