In Magento the button for layout update at CMS > Widgets does not work any longer. According to the Chrome Developer Tools it has to do with javascript and the notice I get is:

Uncaught ReferenceError: WidgetInstance is not definedonclick @ (index):997

What would cause such an error?

2 Answers 2


I had the same problem on Magento Turns out that the page cannot load correctly because of the translation: a string uses invalid characters.

Try switching the admin language to default English and see if the "Layout updates" section loads correctly. If yes, check the error console: the error that you mentioned will not be present any more.

In this case, switch back to your admin language and look for the following error in console: "Uncaught SyntaxError: Unexpected identifier"

Examine the referenced row, it contains the invalid string. Edit/remove it from the translation. Clear cache and reload page. When all invalid characters are removed from the translated string(s), the page will load correctly.


May be your /magento/js/prototype/validation.js is corrupted.

Just replace it with the original version from backup files or from fresh Magento and it will works.

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