var bad_words_array=new Array("badword-1","badword-2","badword-3");
function badwords(txt)
{
var alert_arr=new Array;
var alert_count=0;
var compare_text=txt;

for(var i=0; i<bad_words_array.length; i++>)
{
for(var j=0; j<(compare_text.length); j++)
{
if(bad_words_array[i]==compare_text.
substring>(j,(j+bad_words_array[i].length)).toLowerCase>())
{
alert_count++;
}
}
}
return alert_count;
}

index.html
Contains javascript and HTML code. The form calling Message() function.
<script type=">text/javascript" src=">badwords.js"></script>
<script type=">text/javascript">
function Message()
{
var textbox_val=document.form.textbox.value;
if(textbox_val=="")
{
alert("Please enter a message");
return false;
}
bwords=badwords(textbox_val);
if(bwords>0)
{
alert("Your message contains some bad words please remove it.");
document.form.textbox.focus();
return false;
}
}
</script>
<form action="send.php" method="post"
onsubmit="return Message();" name="form">
<textarea name="textbox"></textarea>
<input type="submit" value=" Submit "/>
</form>