Some people have been having issues listing items in the market over the past few days on the Steam mobile app and desktop browsers. This seems to be happening on browsers that don't have "AppleWebKit" in their user agent string.

Some JavaScript code Valve is using relies on Prototype framework to check the browser the client is using and perform actions based on that.

However, a workaround has been implemented (I think to fix some kind of issue with Scriptaculous library) that sets Prototype to always detect that WebKit is being used. This is done simply by always setting a single variable to true at the beginning of every HTML page.

But there's one typo in this code that breaks the whole thing:

Notice the lowercase K.

It should be:

This leads to a JavaScript error in the Scriptaculous String.prototype.parseStyle method due to an undefined variable (the workaround I mentioned earlier deletes this variable) when trying to sell items on the community market.