Some websites restrict their users to copy any particular item from the site. For this purpose, the websites will usually disable the context menu on their pages which means that the user will not be able to right click on a particular item of the whole page making it impossible to copy anything using the mouse.
<body oncontextmenu="return false;">
There are various studies that suggest that disabling the right click menu and preventing the users from copying or downloading anything from a website is annoying, pointless and unprofessional. But some sites will disable copying of images and others will disable copying or even looking at the website code.
Select Disable for “Active Scripting” under Scripting.
You can drag the above link to your bookmarks toolbar in any browser. And when you encounter disabled right click menu on any page, just click on the bookmarklet and it will instantly enable the right click menu.