[Mediawiki-l] MW 1.17.0 "Expected important but found ie" warnings in Firefox

Brion Vibber brion at pobox.com
Wed Jul 20 18:16:26 UTC 2011

On Wed, Jul 20, 2011 at 9:40 AM, Daniel Barrett <danb at vistaprint.com> wrote:

> Since upgrading to MediaWiki 1.17.0, I'm seeing a host of new warnings in
> Firefox's 3.6's error console, attributed to mediawiki.legacy.commonPrint:
> Warning: Expected 'important' but found 'ie'.
> Source File:
> http://mywiki.net/w/load.php?debug=false&lang=en&modules=mediawiki.legacy.commonPrint%2Cshared%7Cskins.vector&only=styles&skin=vector&*
> Line: 1
> and various others. Are these bugs or a misconfiguration on my end?

These are I believe harmless -- Firefox's classic error console spews a
*lot* of totally irrelevant CSS warnings. This particular bit is about a
pattern that our CSS postprocessing does to handle embedding small images:

  background:url(data:image/png;base64,iVBORw0K....CYII=) center left
center left no-repeat!ie;

A single rule specifying an embeddable file by local path is transformed
into two rules: the first using an embedded data: URI, so most browsers
don't have to make a separate HTTP request to get a tiny icon. The second
line references the original file via an expanded full URL. I believe the
'!ie' on the end is a trick to get other browsers to ignore it, while IE
still takes them. (IE's support for data URIs is missing or broken in some
old versions).

-- brion

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