Cant get onchange to Validate

Question

Hey I'm using the onchange attribute or we they are called, and it wont vailidate in XHTML 1.0 Strict when using the w3c validater which i have to use, i need a way around this so that my code will still work, and validate. the error is: Line 211, Column 32: there is no attribute "onchange"

and here are the values it effects or w/e (not in proper order just cut and pasted)

Cost of Registration:<input id="cost" name="cost" readonly="readonly"/>
<p>
<input type="checkbox" id="monday" name="Attending" value="monday" />Monday<br />
<input type="checkbox" id="tuesday" name="Attending" value="tuesday" />Tuesday<br />
<input type="checkbox" id="wesnesday" name="Attending"value="wednesday"/>Wesnesday<b/></p>

i have another onchange that the validater seems to have no problems with

<p>
 <select id="regcat" onchange="autofill()">
 <option value="UWS Student">UWS Student</option>
 <option value="Student at another institution">Student at another institution</option>
 <option value="UWS Academic">UWS Academic</option>
 <option value="Other UWS Staff">Other UWS Staff</option>
 <option value="Academic from another Institution">Academic from another   Institution</option>
 <option value="Professional">Professional</option>
 <option value="Retired">Retired</option>
</select>
</p>

Can find a fix for this anywhere.(sorry for grammar and spelling its very late)

Answer 1

You need to attach your event handler through JavaScript instead of the attribute. If you're using jQuery:

$('#regcat').change(autofill);

You'll want this in a document ready wrapper if you're not already using one. The shortest way:

$(function() {
    $('#regcat').change(autofill);
});

If you're not using jQuery, you'll use the addEventListener method (but again, you'll need to account for the DOM being ready). If you're not using jQuery AND you need to support IE <9, you'll unfortunately have to also add in the attachEvent call within a conditional comment wrapper.