signed.applets.codebase_principal_support 含义
用 firefox 下载时报如下错误：
此操作被浏览器拒绝！
请在浏览器地址栏输入“about:config”并回车
然后将[signed.applets.codebase_principal_support]设置为'true'
mozilla 官方网站http://kb.mozillazine.org/About:config_entries解释如下：
附录1：
http://kb.mozillazine.org/About:config_entries
Name :
signed. applets. codebase_principal_support
Type :
Boolean
Meaning of Values :
True : Give scripts using codebase principals access advanced scripting capabilities. Setting this preference to "true" is often used to allow IRC websites to gain access to the OS's clipboard at the expense of a security risk.
False (default): Only trusted/signed scripts can access advanced scripting capabilities
Note: file: and resource: schemes are considered "special" and may get extra capabilities regardless of this preference's setting.
附录2：
http://kb.mozillazine.org/Granting_JavaScript_access_to_the_clipboard
Granting JavaScript access to the clipboard
By default, JavaScript is not allowed to read or set your clipboard data for security and privacy reasons. This is because websites scripts can erase and replace what you currently have in your clipboard (data loss issue) and they can read whatever you have in your clipboard (security and privacy issue); as such, you should grant access with caution. There are, however, instances when you might want to bypass this restriction for certain sites. Rich text editors (such as implementations of Mozilla's Midas ) often require access to the clipboard to use copy/paste functions. Other sites may copy useful information to the clipboard for the user to paste elsewhere.
Extension
Instead of manually setting preferences, the AllowClipboard Helper extension manages security policies with a convenient user interface and automates the steps below.
Security policies
You can also enable clipboard access by creating a security policy for the site in question. There is no built-in interface to do this, so you will need to edit user.js . You can also edit about:config , but due to a bug , you will not see the changes you've made (though they will take effect).
Granting to signed scripts
Occasionally the above will not work, as the scripts that need access may use an alternate method of accessing the clipboard. To grant these privileges, which include clipboard access, to signed scripts, set signed.applets.codebase_principal_support to true via about:config . This is not recommended as you cannot limit which sites have these extra privileges.