I agree to the Terms and Conditions
Name
Email
This is an example form. No real submission is made, no info is gathered.
As you see, if the "Agree to terms" checkbox is not checked, the Submit button is disabled.
<script>

//"Accept terms" form submission- By Dynamic Drive
//For full source code and more DHTML scripts, visit http://www.dynamicdrive.com
//This credit MUST stay intact for use

var checkobj

function agreesubmit(el){
checkobj=el
if (document.all||document.getElementById){
for (i=0;i<checkobj.form.length;i++){  //hunt down submit button
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 read/accept terms to submit form")
return false
}
}
}
</script>
Between head of the page
<script>
//change two names below to your form's names
document.forms.Form1.agree.checked=false
</script>
AFTER TAG of the Form html
onClick="agreesubmit(this)"
INSIDE TAG of the checkbox html
disabled.
INSIDE TAG of the submit button