你好，
你可以这样设置
<div style=";>
<div style=";>
<div style="postion:relative;"></div>
</div>
</div>
第三层div “left top”应该在第二层div基础上偏移，即相对于第二层div定位。关于absolute and relative 的介绍，你可以参考这里：
http://www.w3schools.com/cssref/pr_class_position.asp
希望对你有所帮助。
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