<INPUT TYPE="text" NAME="txt1" onkeydown="alert('txt1 click');">
<INPUT TYPE="text" NAME="txt2" onkeydown="if (event.keyCode==13) document.all.txt1.onkeydown();">
<INPUT TYPE="text" NAME="txt2" onkeydown="if (event.keyCode==13) document.all.txt1.onkeydown();">
<INPUT TYPE="text" NAME="text1" value="text1" onkeydown="a()">
<INPUT TYPE="text" NAME="text2" value="text2" onkeydown="if(event.keyCode==13){a()}">