Css selector : How to reference a attribute inside a div

[Kirk]

\[code\] <div id ="group"><img src=http://stackoverflow.com/questions/13758663/' ' id = '1'><img src=http://stackoverflow.com/questions/13758663/' ' id = '2'>.......</div>\[/code\]I would like to reference all the img in the div id 'group' , how to mark it in css? Also, Which is better? Assign all to img / create a class eg. #img.groupItem and reference it everytime? ThanksThe source code:\[code\]<div id="book"><img alt="flip book" src="http://stackoverflow.com/questions/13758663/demo/medium/Web081112_P001_medium.jpg"><img alt="flip book" src="http://stackoverflow.com/questions/13758663/demo/medium/Web081112_P002_medium.jpg"><img alt="flip book" src="http://stackoverflow.com/questions/13758663/demo/medium/Web081112_P003_medium.jpg"></div>\[/code\]After running the javascript:\[code\]<div id="page" style="display: block; width: 1180px; height: 767px; left: 50%; top: 50%; margin: -413.5px auto 0px -590px; cursor: default;"><div id="book" style="position: relative; width: 1180px; height: 767px; transform: translate3d(0px, 0px, 0px);"><div class="turn-page-wrapper" page="1" style="position: absolute; overflow: hidden; width: 590px; height: 767px; top: 0px; right: 0px; left: auto; bottom: auto; z-index: 0; display: none;"><div id="cover" class="turn-page p1" style="width: 590px; height: 767px;"></div></div><div class="turn-page-wrapper" page="2" style="position: absolute; overflow: hidden; width: 590px; height: 767px; top: 0px; left: 0px; right: auto; bottom: auto; z-index: 7;"><div style="position: absolute; top: 0px; left: 0px; overflow: hidden; z-index: auto; width: 968px; height: 968px;"><div class="turn-page p2" style="width: 590px; height: 767px; position: absolute; top: 0px; left: 0px; bottom: auto; right: auto;"><img alt="flip book" src="http://stackoverflow.com/questions/13758663/demo/medium/Web081112_P001_medium.jpg"></div></div></div>\[/code\]The html code is like that for a single img , I used the answer provided here but still not work. I believe this is the problem caused by generate html code?