Optional escape some characters combinations to prevent XSS in old browsers

[hax]

Older versions of Internet Explorer can be tricked into interpreting the page as UTF-7. This can be used for a cross-site scripting attack as the < and > marks can be encoded as +ADw- and +AD4- in UTF-7, which most validators let through as simple text.

See https://code.google.com/p/doctype-mirror/wiki/ArticleUtf7 for more info.