Can I have two JavaScript onclick events in one element?

You can attach a handler which would call as many others as you like:

<a href="#blah" id="myLink"/>

<script type="text/javascript">

function myOtherFunction() {
//do stuff...
}

document.getElementById( 'myLink' ).onclick = function() {
   //do stuff...
   myOtherFunction();
};

</script>

The HTML

<a href="#" id="btn">click</a>

And the javascript

// get a cross-browser function for adding events, place this in [global] or somewhere you can access it
var on = (function(){
    if (window.addEventListener) {
        return function(target, type, listener){
            target.addEventListener(type, listener, false);
        };
    }
    else {
        return function(object, sEvent, fpNotify){
            object.attachEvent("on" + sEvent, fpNotify);
        };
    }
}());

// find the element
var el = document.getElementById("btn");

// add the first listener
on(el, "click", function(){
    alert("foo");
});

// add the second listener
on(el, "click", function(){
    alert("bar");
});

This will alert both 'foo' and 'bar' when clicked.

This one works:

<input type="button" value="test" onclick="alert('hey'); alert('ho');" />

And this one too:

function Hey()
{
    alert('hey');
}

function Ho()
{
    alert('ho');
}

.

<input type="button" value="test" onclick="Hey(); Ho();" />

So the answer is - yes you can :) However, I'd recommend to use unobtrusive JavaScript.. mixing js with HTML is just nasty.