You cannot scroll images continuously using the HTML marquee tag - it must have JavaScript added for the continuous scrolling functionality.
There is a JavaScript plugin called crawler.js available on the dynamic drive forum for achieving this functionality. This plugin was created by John Davenport Scheuer and has been modified over time to suit new browsers.
I have also implemented this plugin into my blog to document all the steps to use this plugin. Here is the sample code:
<head>
<script src="http://code.jquery.com/jquery-latest.min.js" type="text/javascript"></script>
<script src="assets/js/crawler.js" type="text/javascript" ></script>
</head>
<div id="mycrawler2" style="margin-top: -3px; " class="productswesupport">
<img src="assets/images/products/ie.png" />
<img src="assets/images/products/browser.png" />
<img src="assets/images/products/chrome.png" />
<img src="assets/images/products/safari.png" />
</div>
Here is the plugin configration:
marqueeInit({
uniqueid: 'mycrawler2',
style: {
},
inc: 5, //speed - pixel increment for each iteration of this marquee's movement
mouse: 'cursor driven', //mouseover behavior ('pause' 'cursor driven' or false)
moveatleast: 2,
neutral: 150,
savedirection: true,
random: true
});