This plugin has native Joomla 1.5 and 1.6/1.7 support.
It displays simple scroll to top button. Just install and publish the plugin and you'll see a button right after your content.
1. You can define position of button - before, after the content and at the right bottom corner of your browser.
2. You can vary speed of smoothing.
3. Not spoil XHTML 1.0 Transitional valid pages.
4. For Joomla 1.5 you can choose old #top scroll method.