Remove safari predefined button style

media/less/sign/sign.less

@@ -12,6 +12,12 @@
     }
 }
 
+input#signin_b {
+    -webkit-appearance: none;
+    -webkit-border-radius: 5px;
+    border-radius: 5px;
+}
+
 h2 {
     text-align: center;
     margin: 5px auto;