Remove Blue Link Border on Images

Hello all.
I’m using a php code that allows me to pull a random image from a selected folder. Once this image is pulled into my page, I want to have an active link on it to. All is fine, however, this image has a blue border around it in Windows browsers. I tried adding the following to my style sheet:

a img { border:none; }

But it doesn’t seem to be working.

This is the code snippet found inside my main page:
<!— Start of code -->
<a href=“testimonials.php” id=“sidelinks”><?php include “randomimage.php”; ?></a>

<!-- end of code -->

This is the code found on the ‘randomimage.php’
<!-- Start of code -->
<?php

$total = “7”;

$file_type = “.jpg”;

$image_folder = “images/random”;

$start = “1”;

$random = mt_rand($start, $total);

$image_name = $random . $file_type;

echo “<img src=”$image_folder/$image_name" alt="$image_name" />";

?>

<!-- end of the code -->

Ho do I get rid of this pesky border?
Thanks in advance to all.