Secure url for cart, checkout and contacts page

In magento admin put https://domainname/  in secure url
Make "Use Secure URLs in Frontend" as Yes
Then  for checkout in  
/ app /code/core/Mage/Checkout/etc/config.xml file search <secure_url>
Just below Put

           <checkout_cart>/checkout/cart</checkout_cart>
            <checkout_onepage>/checkout/onepage</checkout_onepage>
            <checkout_multishipping>/checkout/multishipping</checkout_multishipping>

And  for contacts in  
/httpdocs/app/code/core/Mage/Contacts/etc/config.xml file
search <frontend>
Just below Put
 <frontend>
               <secure_url>
                       <contacts>/contacts</contacts>
               </secure_url>
</frontend> 

Further if you need more help visit the below url

More Help