Please make sure that Java is activated in your web browser. JMOL is a Java applet and does not run without Java support.
The software is tested with actual versions of Internet Explorer, Firefox and Safari. But it should also work with other up-to-date browers, provided they support Flash and Java.
Please make sure that your Java version is up to date and download the most recent version. Your browser will guide you to the appropriate website.
Two colors are pre-set (Black: default and White: click the 'Background' button near the JMOL window). For other right-click into the JMOL-window and select the colors of your choice by the applet control.
Apple does not support Java on the mobile operating systems. That's why the Java applet JMOL does not run there.