function echeck(str)
{

var at="@"
var dot="."
var lat=str.indexOf(at)
var lstr=str.length
var ldot=str.indexOf(dot)
if (str.indexOf(at)==-1){
alert("This is not Valid E-mail ID")
return false
}

if (str.indexOf(at)==-1 || str.indexOf(at)==0 || str.indexOf(at)==lstr){
alert("This is not Valid E-mail ID")
return false
}

if (str.indexOf(dot)==-1 || str.indexOf(dot)==0 || str.indexOf(dot)==lstr){
alert("This is not Valid E-mail ID")
return false
}

if (str.indexOf(at,(lat+1))!=-1){
alert("This is not Valid E-mail ID")
return false
}

if (str.substring(lat-1,lat)==dot || str.substring(lat+1,lat+2)==dot){
alert("This is not Valid E-mail ID")
return false
}

if (str.indexOf(dot,(lat+2))==-1){
alert("This is not Valid E-mail ID")
return false
}

if (str.indexOf(" ")!=-1){
alert("This is not Valid E-mail ID")
return false
}

return true 
}

function CheckEmailInForm()
{
//var emailID=document.frmSample.CheckEmail
var emailID=document.getElementById("<%=txtto1.ClientID%>");

if ((emailID.value==null)||(emailID.value=="")){
alert("Enter your Email ID")
emailID.focus()
return false
}
if (echeck(emailID.value)==false){
emailID.value=""
emailID.focus()
return false
}
return true
}