js菜鸟求助。

function google_ad_request_done(google_ads) {
var s = '';
var i;/*
* Verify that there are actually ads to display.
*/
if (google_ads.length == 0) {
return;
}
if (google_ads[0].type == "flash" {
   s += '<a href=\"' +
google_info.feedback_url + '\" style="color:000000">Ads by Google</a><br>' +
'<object classid="clsid27CDB6E-AE6D-11cf-96B8-444553540000"' +
' codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,0,0" WIDTH="' +
google_ad.image_width + '" HEIGHT="' +
google_ad.image_height + '"> <PARAM NAME="movie" VALUE="' +
google_ad.image_url + '">' +
'<PARAM NAME="quality" VALUE="high">' +
'<PARAM NAME="AllowScriptAccess" VALUE="never">' +
'<EMBED src="' +
google_ad.image_url + '" WIDTH="' +
google_ad.image_width + '" HEIGHT="' +
google_ad.image_height +
'" TYPE="application/x-shockwave-flash"' +
' AllowScriptAccess="never" ' +
' PLUGINSPAGE="http://www.macromedia.com/go/getflashplayer"></EMBED></OBJECT>';
} else if (google_ads[0].type == "image" {   s += '<a href=\"' +
google_info.feedback_url + '\" style="color:000000">Ads by Google</a><br> <a href="' +
google_ads[0].url + '" target="_top" title="go to ' +
google_ads[0].visible_url + '" onmouseout="window.status=\'\'" onmouseover="window.status=\'go to ' +
google_ads[0].visible_url + '\';return true"><img border="0" src="' +
google_ads[0].image_url + '"width="' +
google_ads[0].image_width + '"height="' +
google_ads[0].image_height + '"></a>';
} else if (google_ads[0].type == "html" {s += google_ads[0].snippet;
} else {
                                s += '<div style="text-align:left;font-weight:bold;font-size:10pt"></div>';
                           if (google_ads.length == 1) {
                                s += '<div style="width:500px;padding-left:0px;margin-top:0px;cursor:hand;font-size:8pt;line-height:12px;"><a href=\"' + google_info.feedback_url + '\" style="color:999;border-bottom:0px #cccccc solid;" class="14Font180">Ads by Google</a></div>'
                                s +='<div style="margin-bottom:4px;width:500px;padding-left:5px;cursor:hand;font-size:10pt;" ' +
                                'onclick="window.open(\'' + google_ads[0].url + '\')" ' +
                                'onmouseout="window.status=\'\';return true;" ' +
                                'onmouseover="window.status=\'' +
                                google_ads[0].visible_url + '\';return true;">' +
                                '<a href="#" style="text-decoration:none;">' +
                                '<span style="font-size:14px;font-weight:bold;text-decoration:underline;color:#ff0000;">' +
                                google_ads[0].line1 + '</span></a><br>' +
                                google_ads[0].line2 + " " + google_ads[0].line3 + '<br>' +
                                '<span style="font-size:12px;color:#008000;">' +
                                google_ads[0].visible_url + '</span></div>'   } else if (google_ads.length > 1) {  /*
  * For text ads, append each ad to the string.
  */
s += '<div style="width:500px;padding-left:0px;padding-bottom:2px;margin-top:0px;cursor:hand;font-size:10pt;line-height:12px;"><a href=\"' + google_info.feedback_url + '\" style="color:999;border-bottom:0px #cccccc solid;"><span style="font-size:10px;"><font color=silver>Ads by Google</font></span></a></div>'for(i = 0; i < google_ads.length; ++i) {                                s += '<span style="padding:5px 0 0 10px;cursor:hand;font-size:14px;color:#000000;line-height:18px;" ' +
                                'onclick="window.open('+"'"+ google_ads.url + "'"+')" ' +
                                'onmouseout="window.status='+"''"+';return true;" ' +
                                'onmouseover="window.status='+"'"+
                                google_ads.visible_url + "'" +';return true;">' +
                                '<span style="text-decoration:underline;font-size:14px;color:#0000ff;font-weight:bold;">' +google_ads.line1 + '</span><br><span style="padding:0 0 0 10px;">' + google_ads.line2 + " " + google_ads.line3 + '</span><br>' +'<span style="padding:0 0 0 10px;color:#008000;font-size:10px;">' + google_ads.visible_url + '</span><br></span>';
          
                  }
         }
    }    document.write(s);
    return;
  }
请解释下上边代码是什么意思。