function checkFile() {
  var fileName = document.getElementById("file").value;
  fileName = fileName.toLowerCase();
  var dotPos = fileName.lastIndexOf('.');
  var fileExt = fileName.substring(dotPos+1);
  var notAllowed = "exe,php,asp,aspx,jsp,out,js,html,com,bat,dll,sh,htm,pl,java,txt";
  var ok = notAllowed.search(fileExt)
  if(ok == -1) return true;
  else {
    alert(fileExt + " files are not allowed.");
    return false;
  }
}
function trim(str){return str.replace(/^\s+|\s+$/g,'');}
function isEmail(str){/*var regex = /^[-_.a-z0-9]+@(([-_a-z0-9]+\.)+(ad|ae|aero|af|ag|ai|al|am|an|ao|aq|ar|arpa|as|at|au|aw|az|ba|bb|bd|be|bf|bg|bh|bi|biz|bj|bm|bn|bo|br|bs|bt|bv|bw|by|bz|ca|cc|cd|cf|cg|ch|ci|ck|cl|cm|cn|co|com|coop|cr|cs|cu|cv|cx|cy|cz|de|dj|dk|dm|do|dz|ec|edu|ee|eg|eh|er|es|et|eu|fi|fj|fk|fm|fo|fr|ga|gb|gd|ge|gf|gh|gi|gl|gm|gn|gov|gp|gq|gr|gs|gt|gu|gw|gy|hk|hm|hn|hr|ht|hu|id|ie|il|in|info|int|io|iq|ir|is|it|jm|jo|jp|ke|kg|kh|ki|km|kn|kp|kr|kw|ky|kz|la|lb|lc|li|lk|lr|ls|lt|lu|lv|ly|ma|mc|md|mg|mh|mil|mk|ml|mm|mn|mo|mp|mq|mr|ms|mt|mu|museum|mv|mw|mx|my|mz|na|name|nc|ne|net|nf|ng|ni|nl|no|np|nr|nt|nu|nz|om|org|pa|pe|pf|pg|ph|pk|pl|pm|pn|pr|pro|ps|pt|pw|py|qa|re|ro|ru|rw|sa|sb|sc|sd|se|sg|sh|si|sj|sk|sl|sm|sn|so|sr|st|su|sv|sy|sz|tc|td|tf|tg|th|tj|tk|tm|tn|to|tp|tr|tt|tv|tw|tz|ua|ug|uk|um|us|uy|uz|va|vc|ve|vg|vi|vn|vu|wf|ws|ye|yt|yu|za|zm|zw)|(([0-9][0-9]?|[0-1][0-9][0-9]|[2][0-4][0-9]|[2][5][0-5])\.){3}([0-9][0-9]?|[0-1][0-9][0-9]|[2][0-4][0-9]|[2][5][0-5]))$/i;*/var regex = /^[-_.a-z0-9]+@[-_a-z0-9]+[.][-_.a-z0-9]+$/i;	return regex.test(str);}

function checkFileForm() {
  if(!checkFile()) return false;

  var cemail, cheading;
  with(window.document.fileForm) {
    cheading = heading;
    cemail = customer_mail;
  }
  
  if(!trim(cheading.value)) {
    alert('Please enter a heading for the file.');
    cheading.focus();
    return false;
  }
  
  if(!isEmail(trim(cemail.value))) {
    alert('Please enter a valid e-mail addess.');
    cemail.focus();
    return false;
  }
  return true;
}