<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>