I asked the same question in the forums for JCE and they provided a solution that works:

These paths are created when the css is compressed, and the Joomla JURI::root(true) method is used to get the correct URL.

There may be an issue with converting this path from the absolute css file path to the relative URL path because of changes Multisites makes to the Joomla path constants.

You can disable the Compression options in the Editor Global Configuration.


Kind regards -Stephan

Can you help us reproducing this issue.
We tried to do it with the JCE 2.4.3 but we are not able to do it.

JMS does NOT modify the really modify the Joomla path constant.
The problem that may happen is that an extension use the realpath() function to get the location of a file on the disk. When using this function, this return the physical location on the disk and not the relative position of the files based on the "document root" directory when a link is created to access the file.

So we would like to be able identifying the PHP source code where is computed.
The issue seems located in the way that the compression is performed.

Also provide some sample of links where we could see the images broken or screenshot.

A Workaround in my configuration and I think in other configurations too:

In the JCE configuration disable the compression of CSS and Javascript, the icon were displayed correctly