Click in the upper menu on Edit / Options. Here choose Content, Enable JavaScript and click OK.
Internet Explorer
Click in the upper menu on Tools / Internet Options.
There click at the menu Securityeither on Medium, or choose Custom Level and then activate below Scripting the point Enable Active Scripting. Confirm by clicking OK.
Mozilla
Click in the upper menu on Edit / Preferences. At Advanced / Scripts & Plugins chooseNavigator. Now click on OK.
Opera
Click in the upper menu on Tools / Preferences. At Advanced / Content choose Enable JavaScript and click OK.