I've created a custom domain for my Salesforce Visualforce page and when I type in  http://enquiry.dacs.org.uk into my browser it goes to https://dacs.secure.force.com/enquiry.

However I'm wanting it to show the page the original URL in the browser (http://enquiry.dacs.org.uk) even though it is displaying the page https://dacs.secure.force.com/enquiry. 

How do I do this?