scusate ho sbagliato script
questo è quello che funziona
[code]<!-- nasconde ai vecchi browser
function ClearForm(form){
form.weight.value = "";

form.height.value = "";

form.bmi.value = "";

form.my_comment.value = "";

form.programma.value = "";

}
function bmi(weight, height) {
bmindx=weight/eval(height*height);
return bmindx;
}
function checkform(form) {
if (form.weight.value==null||form.weight.value.length ==0 || form.height.value==null||form.height.value.length= =0){
alert("\nPer favore, inserisci prima i dati");
return false;
}
else if (parseFloat(form.height.value) <= 0||

parseFloat(form.height.value) >=250||

parseFloat(form.weight.value) <= 0||

parseFloat(form.weight.value) >=250){

alert("\nPer favore controlla i dati inseriti. \nPeso in Kg e \naltezza in cm");

ClearForm(form);

return false;
}
return true;
}
function computeform(form) {
if (checkform(form)) {
yourbmi=Math.round(bmi(form.weight.value, form.height.value/100));
form.bmi.value=yourbmi;
if (yourbmi >40) {

form.my_comment.value="Gravissima obesità";
form.programma.value="Ultimate";

}
else if (yourbmi >35 && yourbmi <=40) {

form.my_comment.value="Grave obesità";
form.programma.value="Ultimate";
}
else if (yourbmi >30 && yourbmi <=35) {

form.my_comment.value="Obesità";
form.programma.value="Ultimate";
}
else if (yourbmi >28.5 && yourbmi <=30) {

form.my_comment.value="Tendente obesità";
form.programma.value="Avanzato";
}
else if (yourbmi >27 && yourbmi <=28.5) {

form.my_comment.value="Forte sovrappeso";
form.programma.value="Avanzato";
}

else if (yourbmi >25.6 && yourbmi <=27) {

form.my_comment.value="Sovrappeso";
form.programma.value="Avanzato";
}
else if (yourbmi >24.2 && yourbmi <=25.6) {

form.my_comment.value="Poco sovrappeso";
form.programma.value="Quickstart Plus";
}
else if (yourbmi >22.7 && yourbmi <=24.2) {

form.my_comment.value="Lieve sovrappeso";
form.programma.value="Quickstart Plus";
}
else if (yourbmi >19.5 && yourbmi <=22.7) {

form.my_comment.value="Peso forma";
form.programma.value="Quickstart Plus";
}
else if (yourbmi >18.5 && yourbmi <=19.5) {

form.my_comment.value="Lieve sottopeso";
form.programma.value="Quickstart Plus";
}
else if (yourbmi <=18.5) {

form.my_comment.value="Sottopeso";
form.programma.value="Quickstart Plus";
}
}
return;
}
// -- fine -->
</script>