When TiddlyWiki goes to save a file, in Firefox, you get the following dialog
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Internet Security

A script from "file://" is requesting enhanced abilities that are UNSAFE and could be used to compromise your machine or data
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### Update:

I now use this:
Type “about:config” into the URL address bar, and set the property security.fileuri.strict_origin_policy to false

user_pref("capability.principal.codebase.p0.granted","UniversalXPConnect  UniversalBrowserRead");
user_pref("capability.principal.codebase.p0.id", "file://");


This advice is almost correct, but you you specify only "file://" you will still get the message. You must specify the full path name of the file. Instead of "file://", give it something like:

user_pref("capability.principal.codebase.p1.granted", "UniversalXPConnect");
user_pref("capability.principal.codebase.p1.id", "file:///C:/Documents and Settings/kevin/Desktop/TwoNote/ScrapBook.html");
user_pref("capability.principal.codebase.p1.subjectName", "");



Firefox no longer accepts that "file://" is good for "file:///blah-blah/blah.html