a href link for entire div in HTML/CSS

Why don't you strip out the <div> element and replace it with an <a> instead? Just because the anchor tag isn't a div doesn't mean you can't style it with display:block, a height, width, background, border, etc. You can make it look like a div but still act like a link. Then you're not relying on invalid code or JavaScript that may not be enabled for some users.

UPDATE 06/10/2014: using div's inside a's is semantically correct in HTML5.

You'll need to choose between the following scenarios:

<a href="http://google.com">
    <div>
        Hello world
    </div>
</a>

which is semantically incorrect, but it will work.

<div style="cursor: pointer;" onclick="window.location='http://google.com';">
    Hello world
</div>

which is semantically correct but it involves using JS.

<a href="http://google.com">
    <span style="display: block;">
        Hello world
    </span>
</a>

which is semantically correct and works as expected but is not a div any more.