Some example form code - html5 input types, validation, etc.

form.html

<form>
  
  <!-- email input type, required - the form won't submit if empty -->
  <input type="email" id="youremail" placeholder="you@example.com" required />
  <label for="youremail">your email</label>
  
  <!-- url input type, optional - form will submit if empty, but if you do enter a value it needs to conform to URL type validation -->
  <input type="url" id="yourwebsite" placeholder="http://example.com" />
  <label for="yourwebsite">your website</label>
  
  <input type="submit" />
</form>

style.css

/* when required form filed is active, make BG pink until it validates */
input:focus:required:invalid  {
  background-color: pink;
}

/* also add an asterisk to indicated required-ness */
input:required + label:before {
  content: "* "; 
}

/* just some basic label styling*/
label {
  color: #888;
  font-style: italic;
}

/* clear after each label */
label:after {
   content: "."; 
   visibility: hidden; 
   display: block; 
   height: 0; 
   clear: both;
}