Quick tip; never use innerHTML (or jQuery’s html()) unless you really want to insert HTML.
Quite often, what you actually want is to insert some text. If this is the case, use innerText (or jQuery’s text()).

Should you need to strip HTML from a string (say you are building a chunk of HTML and need to insert the content of an input-field into it), this is a simple way of doing it:

function stripHtml(str) {
    var temp = document.createElement('DIV');
    temp.innerHTML = str;
    return temp.textContent || temp.innerText;
}

Or, if you’re using jQuery:

function stripHtml(str) {
    return jQuery('<div />', { html: str }).text();
}