<input type='file' name='img1' />
...
<input type='file' name='img8' />

<input type='file' name='img1' id='img1' onblur="check(this.value, this.id');"

try {
      xmlHttp = new XMLHtppRequest();
    } catch (e) {
      var XmlHttpVersions = new Array("MSXML2.XMLHTTP.6.0",
                          "MSXML2.XMLHTTP.5.0",
                        "MSXML2.XMLHTTP.4.0",
                        "MSXML2.XMLHTTP.3.0",
                        "MSXML2.XMLHTTP",
                        "Microsoft.XMLHTTP");
    for(var i=0, i<XmlHttpVersions.lenght && !xmlHttp; i++) {
        try {
          xmlHttp = new ActiveXObject(XmlHttpVersions[i]);
        } catch(e) {}
    }
  }
  if(!xmlHttp)
    alert("Blad podczas tworzenia obiektu XMLHttpRequest");
  else
    return xmlHttp;