var edit_content = new Array("your name",
                             "your e-mail",
                             "subject",
                             "your message");


function check_input(){

var ename=document.feedback.name.value;
var email=document.feedback.mail.value;
var econtent=document.feedback.content.value;
var etext=document.feedback.text.value;
var message="";
var counter=0;

    if((email.indexOf("@")==-1) || (email.indexOf(".")==-1)
    || (email==edit_content[1]))
    {
    message=message+"The e-mail you typed is not valid!";
    counter=counter+1;
    }

    if(ename==edit_content[0])
    {
    message=message+"\nYour name is not valid!";
    counter=counter+1;
    }

    if((econtent==edit_content[2]) || (econtent==""))
    {
    message=message+"\nPlease enter a subject!"
    counter=counter+1;
    }

    if(counter>2)
    {
    message="Please don't spam us!";
    }

    if(message!="")
    {
    window.alert(message);
    window.stop();
    document.feedback.name.focus();
    }
}