>>> re.match('<(?:span|div) id="insert"(?:\s+/)?>(?:.*</(?:span|div))?',text)
>>> text
'<div class="incoming">\n\t<div class="top"><div><span class="author">mots</span><span class="time">23:45</span></div></div>\n\t<div class="next"><p><span class="time">23:45</span>Genug fuer heute...</p></div>\n\t<div id="insert"></div>\n</div>'