function enterNumber(event) {
     if (event.charCode) var charCode = event.charCode;
       else if (event.keyCode) var charCode = event.keyCode;
       else if (event.which) var charCode = event.which;
       else var charCode = 0;
     if ((charCode > 31) && ((charCode < 48) || (charCode > 57))) return false;
   }

   function checkForm() {
     document.getElementById('name_cl').color='';
     document.getElementById('company_cl').color='';
     document.getElementById('mail_cl').color='';
     document.getElementById('phone_cl').color='';
     document.getElementById("warning").innerHTML='';
     var err = false;
     var errMail = false;
     if (!document.getElementById('name').value.match(/[^\s]/g)) {
       document.getElementById('name_cl').color='red';
       document.getElementById("warning").innerHTML = "Please enter your full name.";
       err = true;
     }
     if (!document.getElementById('company').value.match(/[^\s]/g)) {
       document.getElementById('company_cl').color='red';
       document.getElementById("warning").innerHTML = document.getElementById("warning").innerHTML+"<br>Please enter company name, or write 'private.'";
       err = true;
     }
     if (!document.getElementById('mail').value.match(/[^\s]/g)) {
       document.getElementById('mail_cl').color='red';
       document.getElementById("warning").innerHTML = document.getElementById("warning").innerHTML+"<br>Please enter your e-mail address.";
       err = true;
       errMail = true;
     }
     if (!document.getElementById('phone').value.match(/[^\s]/g)) {
       document.getElementById('phone_cl').color='red';
       document.getElementById("warning").innerHTML = document.getElementById("warning").innerHTML+"<br>Please enter your 10-digit phone number.";
       err = true;
     }
     if ((document.getElementById('phone').value.length>0)&&(document.getElementById('phone').value.length<10)) {
       document.getElementById('phone_cl').color='red';
       if (document.getElementById('phone').value.length==1)
         document.getElementById("warning").innerHTML = document.getElementById("warning").innerHTML+"<br>The phone number should be 10-digits long (yours has only "+(document.getElementById('phone').value.length)+" digit).";
       else
         document.getElementById("warning").innerHTML = document.getElementById("warning").innerHTML+"<br>The phone number should be 10 digits (not just "+(document.getElementById('phone').value.length)+" digits).";
       err = true;
     }     
     var re = /[0-9a-z_]+@[0-9a-z_^\.]+\.[a-z]{2,3}/i;
     if ((!errMail)&&(!document.getElementById('mail').value.match(re))) {
       document.getElementById('mail_cl').color='red';
       document.getElementById("warning").innerHTML = document.getElementById("warning").innerHTML+"<br>Please make sure that your e-mail address is correct.";
       err = true;
     }
     if (err) return false
     else return true;
   }