<code>
<!DOCTYPE html>
<html>
<head>
<script>
/*<![CDATA[*/

function Verify(frm){

for (var mess=[],pass=false,z0=1;frm['checkbox'+z0];z0++){

if (frm['checkbox'+z0].checked)
{pass=true;}
}


if (!pass&&!frm['textbox1'].value.replace(/\s/g,'')){
mess.push('1. Please, check at least one of the '+frm['box1'].title +'es or complete the '+frm['textbox1'].title + '.');
}


for (pass=false,z0=0;z0<frm['radio'].length;z0++){

if (frm['radio'][z0].checked){
pass=true;

if (frm['radio'][z0].value=='yes'&&!frm['textbox2'].value.replace(/\s/g,'')){
mess.push('complete '+frm['textbox2'].title);
}
}
}

if (!pass){mess.push('\r\n2. Please, check one of the '+frm['radio'][0].title + ' buttons\u2019.');}

if (mess[0]){
alert(mess.join('\n'));
return false;
}

return true;
}
/*]]>*/
</script>

<script>
function validate(form) {
// Checking if at least one period button is selected. Or not.
if (!form.ambidextrous[0].checked && !form.ambidextrous[1].checked){

alert("3. Please Select \u2018Yes\u2019 or \u2018No\u2019!");
return false;}


if(!form.agree.checked){alert("4. Please check the terms and conditions");
return false; }


return true;
}
</script>
<head>

<body>
<form method="post" onsubmit='return validate(this)'>

<label>1. Please, fill out one of the checkboxes:</label><br>
<input title="checkbox" type="checkbox" name="box1" />
<input type="checkbox" name="box2" />
<input type="checkbox" name="box3" />
<input type="checkbox" name="box4" />
<input title="first &lsquo;text box&rsquo;" name="textbox1" value="" />
<br><br>

<label>2. Please, check one radio button:</label><br>
<input title="&lsquo;radio" type="radio" name="radio" value="yes" />
<input type="radio" name="radio" value="no" />
<input title="second &lsquo;text box&rsquo;" name="textbox2" value="" />
<br><br>

<label>3. Yes or No</label><br>
<input type="checkbox" name="ambidextrous" id="marketing_yes" value='yes' onclick="updateRadioCheckboxes(this);" /><label for="marketing_yes">Yes</label>
<input type="checkbox" name="ambidextrous" id="marketing_no" value='no' onclick="updateRadioCheckboxes(this);" /><label for="marketing_no">No</label><br><br>

<input type="checkbox" name="agree" value='yes'><label>I agree to the <a href="">terms and conditions</a>.</label><br><br>
<!--<input type="submit" value="Submit"> <input type="reset" value="Reset">-->
<input type="submit" name="" value="Submit" onmouseup="Verify(this.form)"/>
</form>

<script>
function updateRadioCheckboxes(checkbox) {
var form = checkbox.form;
if (checkbox == form.marketing_yes) {
form.marketing_no.checked = false;
}
else if (checkbox == form.marketing_no) {
form.marketing_yes.checked = false;
}
checkbox.checked = true
}
</script>
</body>
<html>
</code>