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Source Map Error - Network Error on two scripts - browser-polyfill and content-disposition

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Sudden change of behaviour. On https://www.duolingo.com/ which I have used regularly with FFox, I am now getting a 'white screen' - scripts in the page apparently not firing . FFox debug gives me two errors ...

Source map error: TypeError: NetworkError when attempting to fetch resource. Resource URL: moz-extension://f6fd2f18-0a47-4a31-990a-d869653df191/vendor/browser-polyfill.min.jsSource Map URL: browser-polyfill.min.js.map[Learn More] Source map error: TypeError: NetworkError when attempting to fetch resource. Resource URL: moz-extension://f6fd2f18-0a47-4a31-990a-d869653df191/vendor/content-disposition.min.jsSource Map URL: content-disposition.min.js.map[Learn More]

The Learn More link leaves me even more confused !

I have only noticed this on this web site. I have tried to reinstall with no apparent change. 65.0.2 64 bit Win10

Any ideas welcome

Sudden change of behaviour. On https://www.duolingo.com/ which I have used regularly with FFox, I am now getting a 'white screen' - scripts in the page apparently not firing . FFox debug gives me two errors ... Source map error: TypeError: NetworkError when attempting to fetch resource. Resource URL: moz-extension://f6fd2f18-0a47-4a31-990a-d869653df191/vendor/browser-polyfill.min.jsSource Map URL: browser-polyfill.min.js.map[Learn More] Source map error: TypeError: NetworkError when attempting to fetch resource. Resource URL: moz-extension://f6fd2f18-0a47-4a31-990a-d869653df191/vendor/content-disposition.min.jsSource Map URL: content-disposition.min.js.map[Learn More] The Learn More link leaves me even more confused ! I have only noticed this on this web site. I have tried to reinstall with no apparent change. 65.0.2 64 bit Win10 Any ideas welcome

All Replies (2)

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Hi gw_westdale, I think a Source Map is a feature of the developer tools and not something required to load the page.

However, since you have this URL --

moz-extension://f6fd2f18-0a47-4a31-990a-d869653df191/vendor/browser-polyfill.min.js

You can look up the extension associated with that issue using an internal page: type or paste about:debugging in the address bar, and then use Find (Ctrl+f) to look for f6fd or other part of the unique ID to see what is going on there.

Meanwhile, I notice the site uses a CloudFront server for some of its content. For example, this is the first style sheet address when I load the home page:

https://d35aaqx5ub95lt.cloudfront.net/css/ltr-e3cf191c.css

Can you check to make sure that server isn't being blocked by Firefox's Content Blocking feature or any of your add-ons:

Double-check content blockers: Firefox's Content Blocking feature and extensions that counter ads and tracking may break websites that embed third party content (meaning, from a secondary server).

(A) Do you see a shield icon toward the left end of the address bar, near the lock icon? More info on managing the Tracking Protection feature in this article: Content Blocking.

(B) Extensions such as Adblock Plus, Blur, Disconnect, Ghostery, NoScript, Privacy Badger, uBlock Origin or uMatrix should provide toolbar buttons to manage blocked content in a page. There may or may not be a number on the icon indicating the number of blocked items; you may need to click the button to see what's going on and test whether you need to make an exception for this site.

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Thanks for the help. That did uncover an addon that appears to be dead or blocked. On removing that one, the error messages went away but the site still gave me a 'white page' . Removing more add-ons one by one exposed Norton Safe Web as the culprit - - when that is disabled , DuoLingo.com processes correctly; Norton Safe Web was updated on 11 March so that fits with the start of the problem. I have suggested that DuoLingo get in touch with Norton to see why they are being affected. Thanks again