At a client, I tried to add a “Recently modified items” webpart. The server was set up in English (en-us), while the site was set up in Dutch (nl-nl).

I got an error stating that the webpart couldn’t find the customstrings.js file at _catalogs/masterpages/display templates/language files/nl-nl/customstrings.js?ctag=xxx

When I went to the folder (which you can find at “http://yoursitecollection/_catalogs/masterpages/display templates/language files”) I could see that it had a “En-Us” folder but not a “Nl-Nl” folder.

The quick fix I used was:

– create a new folder called “Nl-Nl” (or the language you want)

– copy the customstrings.js file from the “En-Us” folder to your new folder   

Now, the “recent modified items” shows the actual stuff (and translated in the correct language).

Disclaimer: there is probably a better solution for this, like installing the correct language packs, but this is a quick-fix that works.