function validateForm()
{
var nameField=document.forms["myForm"]["os0"].value;
var emailField=document.forms["myForm"]["os1"].value;
var companyField=document.forms["myForm"]["os2"].value;
var arrivalDateField=document.forms["myForm"]["os3"].value;
var departureDateField=document.forms["myForm"]["os4"].value;
var atpos=emailField.indexOf("@");
var dotpos=emailField.lastIndexOf(".");
var arrDateCon=arrivalDateField.lastIndexOf("20");
var depDateCon=arrivalDateField.lastIndexOf("20");

if (nameField==null || nameField=="")
  {
  alert("Please enter the name of attendee");
  return false;
  }

if (emailField==null || emailField=="" || atpos<1 || dotpos<atpos+2 || dotpos+2>=emailField.length)
  {
  alert("Please enter a valid e-mail address");
  return false;
  }

if (companyField==null || companyField=="")
  {
  alert("Please enter the name of your company");
  return false;
  }

if (arrivalDateField==null || arrivalDateField=="" || arrDateCon<1 || arrivalDateField=="E.g. 12 Jan 2012")
  {
  alert("Please enter the full date of arrival");
  return false;
  }

  
if (departureDateField==null || departureDateField=="" || depDateCon<1 || departureDateField=="E.g. 13 Jan 2012")
  {
  alert("Please enter the full date of departure");
  return false;
  }

}

function clear_textbox1()
{
if (document.forms["myForm"]["os3"].value == "E.g. 12 Jan 2012")
document.forms["myForm"]["os3"].value = "";
} 

function clear_textbox2()
{
if (document.forms["myForm"]["os4"].value == "E.g. 13 Jan 2012")
document.forms["myForm"]["os4"].value = "";
}