本章介绍怎么根据id与class查找标签。假设有下面的HTML文档：
htmlheadtitleAsimpleexamplepage/title/headbodydivpclass="inner-textfirst-item"id="first"Firstparagraph./ppclass="inner-text"Secondparagraph./p/divpclass="outer-textfirst-item"id="second"bFirstouterparagraph./b/ppclass="outer-text"bSecondouterparagraph./b/p/body/html复制
可以通过URL