Adding Inline Search function to web page

If I understand your question, you are asking if it is possible to allow a user to type in a query that will search the text of page they are on?

You can certainly do that. I would suggest looking into one of the javascript libraries, jQuery is my library of choice, for your functionality. It has a rich selector syntax that allows you to search various parts of the page easily and without worrying about cross-browser coding yourself.