<form action="/file-upload"
      class="dropzone"
      id="my-awesome-dropzone">
    <div class="dz-message needsclick">
        Drop files here or click to upload.<br />
        <span class="note needsclick">(This is just a demo dropzone. Selected files are <strong>not</strong> actually uploaded.)</span>
    </div>
</form>

<!-- ========== JS ========== -->
<script>
    $(function($) {
        Dropzone.options.myAwesomeDropzone = {
          paramName: "file", // The name that will be used to transfer the file
          maxFilesize: 5, // MB
          accept: function(file, done) {
            if (file.name == "justinbieber.jpg") {
              done("Naha, you don't.");
            }
            else { done(); }
          },
          dictDefaultMessage: "Drop files here or click to upload."
        };
    });
</script>