CSS after清除浮动
例如：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title><style>.clear{zoom:1;}.clear:after {display:block; clear:both; content:" "; visibility:hidden; height:0; line-height:0;}</style></head><body><div style=" border:1px solid #6F0;" "; visibility:hidden; height:0; line-height:0;}