function checkAdd() {
   var error=false;
   var m="";
   if (document.addillu.file.value==""){
      m="- An input file is needed";
      error=true;
   }
   else
   {
      var pathfile = document.addillu.file.value;
      var filename = pathfile.substring(pathfile.lastIndexOf("\\")+1);
      if(filename.indexOf(' ') == -1)
      {
          var fileext = filename.substring(filename.lastIndexOf('.')+1);
          var fileTypes = '|gif| |jpg| |jpeg| |png|';
          fileext = '|' + fileext + '|';  
          if (fileTypes.indexOf(fileext) == -1){
             m=m+"\n- The input file is not a valid image (gif, jpg, jpeg, png)";
             error = true;            
          }
      }
      else
      {
          m=m+"\n- The input file name cannot contain any space";
          error = true;      
      }
   }
   if (error)
      alert(m);
   else
      document.addillu.submit();
}