You can use Javascript code to customize the functionality and appearance of a survey.
How to get the correct element code
You can target specific elements in javascript with element code p0e0 (page 0, element 0).
This calculation always begins from 0, so first page is p0 and first element on a given page is e0. So for example fourth element on third page would be p2e3. You must count every element, also image and text elements. More information here.
How to add Javascript to your survey
1. Open your survey and go into Build-view and click Settings
2. On the window that opens click 'Snippets' and insert your code into the 'Body bottom:' text box.
jQuery is available for the snippets. It's a good practice to put your script inside a ready handler to ensure that the document has fully loaded before the script is run.
<script>
jQuery(document).ready(function(){
//Your code here
});
</script>