I'm working on an HTML5 extension for Photoshop. When I include the HTML5 "range" element (i.e. a slider):
<input type="range" min="0" max="10"/>
According to Davide Barranca on Twitter, this is a known bug without an ETA fix. The slider has to be styled explicitly.
You can use topcoat's explicit styling to make the slider show up: range/desktop-light.css at master · topcoat/range · GitHub