New ASPX page, and practice div layout and table layout

1, Div centered horizontally:

<div style="margin:0px auto;width:100px;height:100px;background:#FF0000;">

 

 2, div arranged horizontally

<div style="float:left; width:20%; height:100px; background:#FF0000;"></div>
    <div style="float:left; width:60%; height:200px; background:#000000;"></div>
    <div style="float:left; width:20%; height:100px; background:#FF0000;"></div>

 

 3,