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This rule in a userstylesheet I use seem to affect it:

*[id*='related'], *[id*='side'], *[role*="complementary"], *[id*='Panel'],  *[id*='Layout'] {
    visibility:hidden !important;


enter image description here

So, is there any documentation of its HTML?

Edit:: And can I exclude it by @-moz-document regexp()?

Workaround:: prefix body on all selectors (body [id*='related'],...) to restrict applying only on webpages. (apparently sidebar doesn't live inside a <body> tag) demo

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up vote 1 down vote accepted

Firefox's interface is written in XUL which is a form of XML. It's markup is almost identical to HTML with some other advantages, particularly for add-on devs.

To view the code that constructs the user interface, open a new tab and go to chrome://browser/content/browser.xul. This will display your web browser's interface inside the web browser. Then, use Firefox's built-in web dev tools to inspect the markup or press Ctrl+U to view the source.

It's so damn easy to edit, even for someone with little to no programming knowledge. This is why I love Firefox. You can live-edit the CSS and when you're happy with the changes, use Stylish to make a new style (blank style, using the XUL namespace) and save it.

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