IE Error: HELP! "'This page contains both secure and..."

Hi There, I require assistance in ensuring the error/warning: 'This page contains both secure and nonsecure items', does not appear on any of my site pages when visitors browse using Internet Explorer (IE). This past weekend I identified the major culprit I believe, which was a Client Login button that appears on 99% of the pages within my website. This message occurs when customers attempt to view a webpage using https that contains information linked using http. This happens when using the full URL when linking to images or including files. Since I isolated the cause, I adjusted the code to a virtual link. (src='images/[login to view URL]') The only issue I have now is that the client login button is not appearing on the "contact us" page and the error still appears at homepage 'This page contains both secure and nonsecure items', but im not getting it on any other pages. I absolutely have to make sure NO VISITORS GET THIS ERROR WHEN THEY LAND ON THE HOMEPAGE or OTHER PAGES. Please advise. Thank you.