When a calling a page such as html/php/asp/aspx/cfm, the page contents like pictures, sound, javascripts, flash are loaded to render the page on browser. If any of these are called over an http:// connection while the main page is over https:// this warning [crossed-out padlock] will be displayed in browser to visitor.
The warning indicates to the visitor that all the page components not secure/encrypted. Hence the main page contains un-secure / non-encrypted content, even though the main page is being called over a secure url (https://).
Please correct your code such that all page components are called over https:// connections only.
