Railgun is a WAN optimization technology that we offer our hosting customers in partnership with a company called CloudFlare.
CloudFlare’s Railgun technology greatly speeds up the delivery of non-cached pages. While CloudFlare automatically caches 65% of the resources needed to make up a page, 35% can't be cached because the resources are dynamically generated or marked as 'do not cache'. That 35% is often the initial HTML of the page that must be downloaded first. CloudFlare Railgun speeds this remaining 35%.