试了几个FireFox扩展

1.Better Gmail 0.6.1
　　改皮肤的功能不错，鼠标到哪里，哪封信就加亮。
　　label color
　　macro
2.Clipmarks 2.0.4
　　作用是方便选中网页中的某一处，然后复制。
　　似乎让机器变慢了，且需要登录。禁用。
3.Download Statusbar 0.9.4.6
　　在状态栏显示当前下载状态，可以停止/继续。
4.United States English Dictionary 2.0.0.6
　原以为是词霸类的软件。用于拼写检查。 禁用。
" This extension packages a subset of the original English wordlist created by Kevin Atkinson for Pspell and Aspell and thus is covered by his original LGPL license. The affix file is a heavily modified version of the original english.aff file which was released as part of Geoff Kuenning's Ispell and as such is covered by his BSD license."［ http://www.blogzilla.info/spellchecker/］