那你就把 循环迭代的结果全部 存入一个 字符串 在一次 写出var s="";
for(i=1;i<a.length-2;i=i+3) {                  
                s+="<div align=left class=news><a href=\"http://www.qzhsoft.com.cn/NewsInfo.asp?id="
                +a[i].replace(/^\s+|\s+$/g,'')+"\" title=\""+a[i+1]+"\" target=_ablank><span>"+a[i+1].substring(0,18)
                +"<\/span><\/a>"+a[i+2]+"<br><\/div> 
             }
             
        }    document.write(s)