After a new version of the site is deployed, the first time every user opens the site, none of the site's stylesheets are downloaded or load. Refreshing the page downloads and loads the stylesheets and then the site looks fine until the next time we do a deployment.
The site is a .NET 4 MVC website deployed to Windows Server 2008 R2 running IIS 7. The site is deployed using a publish package created through VS10 and imported into IIS.
Most users access the site using IE10 or 11 and some earlier IE users. None of the pcs available to test on have Firefox or Chrome, so I haven't been able to test whether the site's styles show up on first load in other browsers. Locally, the site displays correctly regardless of the browser and version used. There are no server errors or browser errors reported.
The styles are Bootstrap, and a custom site stylesheet.