title: Determine if the page has changed using Webdriver
body: <p>Sometimes web pages' visible content depends on the page input elements state (for example, input element 'Choose your university' may appear only after you have chosen 'Student' in 'Job' field) or on clicking some page elements (like dropdown menu buttons). I am trying to automate the process of finding out such page elements dependencies using Selenium Webdriver. The first idea is to enter some stuff in text input fields, set checked/unchecked checkboxes, click some buttons/links, etc. and see if any elements on the page have appeared/disappeared. The problems are:</p>
  
  <ul>
  <li><p>Is there an easy way to find out if something on the page has appeared? Well, I could make a map from web page elements to {'visible', 'invisible'} states after each change and find out if something has changed, but is there something built-in for this purpose?</p></li>
  <li><p>Clicking some buttons might cause loading another page, and I want to stay in withing the page I am testing, is there a way to determine if click() method will cause loading another page and prevent it?</p></li>
  </ul>