Safari crash on mismatched tags

If Apple's mac web browser, Safari, crashes on your web page, look for mismatched beginning and end tags. With a fairly complex page, using lots of CSS, we found that Safari was crashed by a simple mismatch of h1 (opening) and h2 (closing) tags ... note that we first debug-interpolated the error to the CSS file, but there was no error to fix ... the typo was in HTML that used the CSS file ...

(keywords: crash, crashes, crashed, safari browser)