75190 highlight terms javascript

We need a Javascript function that highlights given terms in the page HTML body. The desired look and feel can be seen when searching for something on Google, then viewing the cached page with all search terms highlighted. The function must work at least Internet Explorer 5 and newer and Netscape 6 and newer and degrade gracefully (without errors) on non-compatible older browser. We do not want separate code for each browser, but unified standards-conform Javascript code that uses DOM access methods. The highlighting shall be done by wrapping the search term in em tags so that all em em tags can be formatted by CSS. The highlighting must not alter the text or appearance of the page other than inserting em tags. The Javascript source must be consistently formatted and commented. Your work must not contain any proprietary, stolen or copyright protected third-party code. We require full copyright to all sources to be able to modify and extend the code by ourselves in the future, should the need arise. If the project is completed successfully, there is a good change that we build up a a long-term working relationship with you. This means you may get credited in the software's about page and/or by a link from our website.