var checkobj

function agreesubmit(el){
checkobj=el
if (document.all||document.getElementById){
for (i=0;i<checkobj.form.length;i++){  
var tempobj=checkobj.form.elements[i]
if(tempobj.type.toLowerCase()=="submit")
tempobj.disabled=!checkobj.checked
}
}
}

function defaultagree(el){
if (!document.all&&!document.getElementById){
if (window.checkobj&&checkobj.checked)
return true
else{
alert("Please select a product")
return false
}
}
}