Código HTML:
<table border="0" align="center"> <tr> <td colspan="3"> <center><textarea style="color: ffffff; background: 3300cc" id="ayuda" name="ayuda" cols="23" rows="6"></textarea></center> </td> </tr> <tr> <td colspan="3"> <input type="checkbox" name="colores" onmouseover="ayuda.value ='cambia la combinacion de colores'" onmouseout="ayuda.value =''" onClick="if(this.checked) {?}"> </td> </tr> </table>