images not working in IE-9 and below

I check the mark up on W3 and got this error message `Line 698, Column 457: Element link is missing required attribute property.
<link rel=’stylesheet’ id=’slideshow-jquery-image-gallery-stylesheet_functional-css’ href=’https://www.acornpropertysolutions.com/wp-content/plugins/slideshow-jquery-image-gallery/style/SlideshowPlugin/functional.css?ver=2.2.19&#8242; type=’text/css’ media=’all’ />

`

could this be causing the problem?