How to disable right-click context-menu in JavaScript
Capture the onContextMenu event, and return false in the event handler.
You can also capture the click event and check which mouse button fired the event with event.button, in some browsers anyway.
If you don't care about alerting the user with a message every time they try to right click, try adding this to your body tag
<body oncontextmenu="return false;">
This will block all access to the context menu (not just from the right mouse button but from the keyboard as well)
However, there really is no point adding a right click disabler. Anyone with basic browser knowledge can view the source and extract the information they need.