"insert/modify image" icon doesn't produce image on page

I've tried using the "insert/modify image" icon to put an extra image on my description page to no avail. My store is working normally and I wanted to add an extra image to and item. I put a the URL "https://www.dropbox.com/s/813amfiurwqr7sk/mickey.gif" in and can't get a preview in the preview box and all I get is an icon on my page. My administrator is no longer available to me and I'm not too good with code. Am I doing something wrong? URL for the item i'm editing is "www.rwc-3.com/vinylstickers/lenlin541/product.php?page=1&product_type=1&cPath=1&pID=2&action=new_product"

Switch to the text editor mode and enter the image code

Using the insert image function uses your admin as the base ref