<!DOCTYPE html> <meta charset="utf-8"> <title>CSS Transitions Test: transition-duration - negative number</title> <link rel="author" title="Intel" href="http://www.intel.com"> <link rel="author" title="Shiyou Tan" href="mailto:shiyoux.tan@intel.com"> <link rel="help" title="2.2. The 'transition-duration' Property" href="http://www.w3.org/TR/css3-transitions/#transition-duration-property"> <meta name="assert" content="A negative value for 'transition-duration renders the declaration invalid which means the transition is immediate."> <style> div { height: 100px; transition-property: width; transition-timing-function: linear; width: 100px; } #ref { background-color: yellow; transition-duration: 2s; } #test { background-color: blue; transition-duration: -2s; } </style> <body> <p>Click the 'Start' button below. Test passes if the width of yellow square grows smoothly but the blue grows immediately.</p> <div id="ref"></div> <div id="test"></div> <button>Start</button> <script> (function() { var button = document.querySelector("button"), test = document.querySelector("#test"), ref = document.querySelector("#ref"); button.addEventListener("click", function(evt) { test.setAttribute("style", "width: 200px;"); ref.setAttribute("style", "width: 200px;"); }, false); })(); </script> </body>