Use CSS to control the left and right arrangement of pages

In the content page of the website, I placed the 300*250 advertisement in the upper left corner, using the CSS floating <div style= "float:left;margin-right:15px;" ", because of the characteristics of CSS, this setting, when the height of the article more than 250 pixels, the article automatically moved to the bottom of the ads, instead of the left and right two columns, how to separate? So we give this div a vertical height <div style= "float:left;margin-right:15px;height:300px" > This height value set to how much, according to the needs of the page to adjust themselves.

In fact, this is similar to using CSS to draw a rectangle, you need to set the border color and width, look at the following example:

Draw rectangle: <div style= "width:300px;height:150px;border:1px solid #000 ″></div>

Draw vertical line (above example put middle): <div style= "width:300px;height:150px;border:1px solid #000 ″><div style=" Width:150px;height : 150px;border-right:1px Solid #000 ″></div></div>