Bootstrap 3 went mobile-first, which means that browsers that don't support media queries got much more complicated to support. The Bootstrap documentation recommends using Respond.js, but this often introduces performance issues and other bugs.
This is a "desktop-only" version of Bootstrap, which has all media queries stripped from it, and serves the "medium" version of Bootstrap (simulating a 1024px wide display).
Use conditional comments to load the desktop version of Bootstrap for MSIE 8 and below:
<!--[if gt IE 8]><!-->
<link href="path/to/bootstrap.css" rel="stylesheet" />
<!--<![endif]-->
<!--[if lt IE 9]>
<link href="path/to/bootstrap-desktop.css" rel="stylesheet" />
<![endif]-->
Whenever a new version of Bootstrap is released, I run the released CSS through a build process that regenerates it using grunt-stripmq. For more information, see my blog post explaining this project.