document.write("<li><a href=\"intro.htm\" target=\"_self\">产品概况</a>");
document.write("<li><a href=\"intro_features.htm\" target=\"_self\">基本信息</a>");
document.write("<li><a href=\"intro_tech.htm\" target=\"_self\">产品用途</a>");
document.write("<li><a href=\"intro_demo.htm\" target=\"_self\">成功案例</a>");