navyspitfire on "Next post/prev post link image rollover"

I checked some other responses but couldn't find what I am looking for. Just trying to swap images on rollover. Not sure why this code isn't working.

<div class="port-nav left">
			<p class="prev"><?php previous_post_link('%link', '<img src="/wp-content/themes/starkers-child/img/LeftArrow_Idle.png" alt="Previous" />'); ?></p>
			<p class="next"><?php next_post_link('%link', '<img src="/wp-content/themes/starkers-child/img/RightArrow_Idle.png" alt="Next" />'); ?></p>
		</div>

.port-nav {
	margin: 2em 0 0 0;
}

.port-nav p {
	display: inline-block;
}

.port-nav p:first-child {
	margin-right: 0.5em;
}

.port-nav .next:hover {
	background: url(/wp-content/themes/starkers-child/img/RightArrow_RollOver.png);
	display: block;
}