function friendecheck(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("Your friend email address is invalid.")
return false
}

if (str.indexOf(at)==-1 || str.indexOf(at)==0 || str.indexOf(at)==lstr){
alert("Your friend email address is invalid.")
return false
}

if (str.indexOf(dot)==-1 || str.indexOf(dot)==0 || str.indexOf(dot)==lstr){
alert("Your friend email address is invalid.")
return false
}

if (str.indexOf(at,(lat+1))!=-1){
alert("Your friend email address is invalid.")
return false
}

if (str.substring(lat-1,lat)==dot || str.substring(lat+1,lat+2)==dot){
alert("Your friend email address is invalid.")
return false
}

if (str.indexOf(dot,(lat+2))==-1){
alert("Your friend email address is invalid.")
return false
}

if (str.indexOf(" ")!=-1){
alert("Your friend email address is invalid.")
return false
}

return true
}

function ownecheck(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("Your own email address is invalid.")
return false
}

if (str.indexOf(at)==-1 || str.indexOf(at)==0 || str.indexOf(at)==lstr){
alert("Your own email address is invalid.")
return false
}

if (str.indexOf(dot)==-1 || str.indexOf(dot)==0 || str.indexOf(dot)==lstr){
alert("Your own email address is invalid.")
return false
}

if (str.indexOf(at,(lat+1))!=-1){
alert("Your own email address is invalid.")
return false
}

if (str.substring(lat-1,lat)==dot || str.substring(lat+1,lat+2)==dot){
alert("Your own email address is invalid.")
return false
}

if (str.indexOf(dot,(lat+2))==-1){
alert("Your own email address is invalid.")
return false
}

if (str.indexOf(" ")!=-1){
alert("Your own email address is invalid.")
return false
}

return true
}

function form_validation()
{
    valid = true;

    if ( (document.share_email_form.email_to.value == "") && (document.share_email_form.email_from.value == "") )
    {
        alert ( "Please fill in the 'To:' and 'From:' boxes." );
        valid = false;
    }

    else {

    if ( document.share_email_form.email_to.value == "" )
    {
        alert ( "Please fill in the 'To:' box." );
        valid = false;
    }

    if ( document.share_email_form.email_from.value == "" )
    {
        alert ( "Please fill in the 'From:' box." );
        valid = false;
    }

   }

var emailto=document.share_email_form.email_to;

if (friendecheck(emailto.value)==false){
emailto.value="";
emailto.focus();
valid = false;
}

var emailfrom=document.share_email_form.email_from;

if (ownecheck(emailfrom.value)==false){
emailfrom.value="";
emailfrom.focus();
valid = false;
}

    return valid;
}