diff --git a/app.py b/app.py
index 808c04c..0f29ceb 100644
--- a/app.py
+++ b/app.py
@@ -66,7 +66,16 @@ def fetch_mf2(url):
         default=False,
         help="Run application in debug mode",
     )
+    parser.add_option(
+        "-p",
+        "--port",
+        action="store",
+        type="int",
+        dest="port",
+        default=8080,
+        help="Change dev server port (default is 8080)",
+    )
     (options, args) = parser.parse_args()
 
     if options.debug:
-        app.run(debug=True, port=8080)
+        app.run(debug=True, port=options.port)
diff --git a/templates/index.jinja2 b/templates/index.jinja2
index 8391093..57e5a10 100644
--- a/templates/index.jinja2
+++ b/templates/index.jinja2
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
 <head>
   <meta charset="utf-8">
   <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
@@ -52,7 +52,7 @@
     <form action="/" accept-charset="UTF-8" method="get">
       <div class="form-group">
         <label for="url">Enter a URL</label>
-        <input id="url" class="form-control form-control-lg" type="url" name="url"  placeholder="https://example.com/person.html" />
+        <input required id="url" class="form-control form-control-lg" type="url" name="url" placeholder="https://example.com/person.html" />
       </div>
 
       <div class="form-group">
@@ -79,17 +79,17 @@
     <form method="post" action="/" class="mb-5">
       <div class="form-group">
         <label for="doc">HTML</label>
-        <textarea id="doc" name="doc" rows="6" class="form-control form-control-lg"></textarea>
+        <textarea required id="doc" name="doc" rows="6" class="form-control form-control-lg"></textarea>
       </div>
 
       <div class="form-group">
-        <label for="url">Base URL</label>
-        <input id="url" name="url" type="url" class="form-control form-control-lg" />
+        <label for="base-url">Base URL</label>
+        <input id="base-url" name="url" type="url" class="form-control form-control-lg" />
       </div>
 
       <div class="form-group">
-        <label for="parser">Parser</label>
-        <select id="parser" name="parser">
+        <label for="doc-parser">Parser</label>
+        <select id="doc-parser" name="parser">
           <option>html5lib</option>
           <option>lxml</option>
           <option>html.parser</option>
