HTML images are too small in IE 7/8

I generated some static images 开发者_如何学Gofrom PHP, my code looks like this:

echo "<img src='http://192.168.1.5/admin/" . $row['location'] . "' alt='image' />";

It works fine in Firefox/IE9/Chrome but in IE8 and below, the images show up tiny.

I tried changing the size value to auto:

echo "<img src='http://192.168.1.5/admin/" . $row['location'] . "' alt='image' height='auto' width='auto' />";

However, the images refused to display at all in IE9 and below. Is there a way to get these images to show up normally in versions below 8?