html编码转换

http://webdesign.about.com/od/localization/l/blhtmlcodes-math.htm

http://www.cnblogs.com/terryglp/articles/1900503.html

http://www.december.com/html/spec/codes.html

http://e.v-get.com/tool/code_ascii.html

http://blog.csdn.net/czhphp/article/details/18311303