Do you use Respond JS to target IE8 with Bootstrap?
By default, we do not accommodate IE8 or lower, but should it arise as a specific requirement, then you can include Respond JS in your application, after Bootstrap. Respond JS enables responsive web designs in browsers that don't support CSS3 Media Queries.
Note: Respond JS will be included in a new MVC5 Web Application. If you are working on an existing application, you can get it from NuGet or https://github.com/scottjehl/Respond.