Form approach
As scoota269 says, you should use onSubmit instead, cause pressing enter on a textbox will most likey trigger a form submit (if inside a form)
<form action="#" onsubmit="handle">
<input type="text" name="txt" />
</form>
<script>
function handle(e){
e.preventDefault(); // Otherwise the form will be submitted
alert("FORM WAS SUBMITTED");
}
</script>
Textbox approach
If you want to have an event on the input-field then you need to make sure your handle() will return false, otherwise the form will get submitted.
<form action="#">
<input type="text" name="txt" onkeypress="handle(event)" />
</form>
<script>
function handle(e){
if(e.keyCode === 13){
e.preventDefault(); // Ensure it is only this code that runs
alert("Enter was pressed was presses");
}
}
</script>