function advertisement_form(form)
{
  // validate name
  if(form.name.value == ""){
    alert("Name is a required field")
    form.name.focus();
    return false;
  }
  
  if (form.email.value == ""){
    alert("Your e-mail is a required field")
    form.email.focus();
    return false;
  }
  
  if (form.telephone.value == ""){
    alert("Telephone is a required field")
    form.telephone.focus();
    return false;
  }
  
 if (form.telephone.value.search(/\d\d\d\d\d\d\d\d\d\d/)){
    alert ("The telephone number that you have enterd is not valid.\r\nPlease enter the telephone number with the format xxxxxxxxx.\r\nE.g 0123455345.")
    form.telephone.focus();
    return false;
  } 
  
  if (form.message.value == ""){
    alert("Message is a required field")
    form.message.focus();
    return false;
  }
  
  if(validateEmail(form.email.value) == false){
    alert("Email format is invalid")
    form.email.focus();
    return false;
  }
  
  function validateEmail( strValue) {
    var objRegExp = /(^[a-z]([a-z_\.]*)@([a-z_\.]*)([.][a-z]{3})$)|(^[a-z]([a-z_\.]*)@([a-z_\.]*)(\.[a-z]*))/i;
    
    //check for valid email
    return objRegExp.test(strValue);
  }
}