<script>
function stampaValore(valore) {
alert(valore);
}
</script>
<table border="1">
<tr><td onclick="stampaValore(this.innerHTML)">val 1</td></tr>
<tr><td onclick="stampaValore(this.innerHTML)">val 2</td></tr>
<tr><td onclick="stampaValore(this.innerHTML)">val 3</td></tr>
<tr><td onclick="stampaValore(this.innerHTML)">val 4</td></tr>
</table>