#include "String.au3"
$str = '<span class="js-txt js-title notify-message_title_text notify-message_title_text_error"> <b>тут текст </b></span>'
$aOut = _StringBetween($str, '<span class="js-txt js-title notify-message_title_text notify-message_title_text_error">', '</span>') ; Раз
ConsoleWrite($aOut[0] & @LF)
$aOut = StringRegExp($str, '<span .*?>(.*?)<\/span>', 3) ; Два
ConsoleWrite($aOut[0] & @LF)