<a   href="xx.xx"   id=pic1   onclick="savepic();return   false;"   style="cursor:hand">点击下载</a>   
          <script>   
                  function   savepic()
                {   
                  if(document.all.a1==null)
                        {   
                                  objIframe=document.createElement("IFRAME");   
                                  document.body.insertBefore(objIframe);   
                                  objIframe.outerHTML=   "<iframe   name=a1   style='width:0;hieght:0'   src="+pic1.href+"></iframe>";   
                                  re=setTimeout("savepic()",1)   
                          }   
                 else
                        {   
                                  clearTimeout(re)   
                                  pic   =   window.open(pic1.href,"a1")   
                                  pic.document.execCommand("SaveAs")   
                                  document.all.a1.removeNode(true)   
                          }
                }   
          </script> 
      注： href="xx.xx"  为下载文件的地址,比如 href="logo.gif"、href="logo.rar"