Javascript Validation

function check()
{
if(document.getElementById("<%=txtfname.ClientID%>").value == "")
{
alert ('Please enter first name');
return false;
}
else
{
if(document.getElementById("<%=txtlnm.ClientID%>").value == "")
{
alert ('Please enter last name');
return false;
}
else
{
if(document.getElementById("<%=txtemail.ClientID%>").value == "")
{
alert ('Please enter email ID');
return false;
}
else
{
if(emailValidator(document.getElementById("<%=txtemail.ClientID%>"), "Invalid EmailID"))
{
return true;
}
else
{
if(document.getElementById("<%=txtpswrd.ClientID%>").value == "")
{
alert ('Please enter password');
return false;
}
else
{
var psword = document.getElementById("<%=txtpswrd.ClientID%>");
if(passwordValidator(psword,"Invalid Password. Enter Password as 4 digit birth year and last 4 digits of SSN "))
{
return true;
}
else
{
return false;
}
}
}
}
}
}
}
}

function emailValidator(elem, helperMsg)
{
var emailExp = /\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*/;
if (elem.value != "")
{
if(elem.value.match(emailExp))
{
}
else
{
alert(helperMsg);
elem.focus();
return false;
}
}
}

function passwordValidator(elem, helperMsg)
{
var passwordExp = /^[0-9]+$/;
if(elem.value != "")
{
if(elem.value.match(passwordExp))
{
return true;
}
else
{
alert(helperMsg);
elem.focus;
return false;
}
}
}