Awesome

Bootstrap 3 for IE7

Bootstrap 3 dropped support for Internet Explorer 7, but you can add it back by simply adding this conditional CSS.

<!--[if lt IE 8]>
    <link href="/css/bootstrap-ie7.css" rel="stylesheet">
<![endif]-->

Bootstrap 3 uses the box-sizing property for layouts which is not natively supported by IE7. The polyfill 'boxsizing.htc' is required: https://github.com/Schepp/box-sizing-polyfill

Percentage width rounding issue Info
As this is only a CSS stylesheet there may be problems with using Bootstrap 3's JavaScript in IE7.
Some elements rely on pseudo-selectors which IE7 does not support (first-child, last-child etc)

Q. Do I need to make any changes to my HTML to add support for bootstrap3-ie7?

A. Nope! Just include the conditional IE7 stylesheet and you're ready to go!
Q. Does this include the new Glyphicons introduced in Bootstrap 3.3.2?

A. Yep!
Q. What about rounded corners, box shadows and gradients for IE7. How can I get those?

A. You could use CCS3Pie for adding support for those CSS3 properties to older IE. http://css3pie.com/. If you use that you can add this to your CSS to quickly add border-radius https://gist.github.com/coliff/5618329
Q. Is the CSS available on a CDN?

A. Yes, thanks to JSDelivr: https://cdn.jsdelivr.net/gh/coliff/bootstrap-ie7/css/bootstrap-ie7.min.css, however the box sizing polyfill requires the CSS to be hosted locally so the layout will be broken if you serve the CSS from a CDN.
Q. What about Internet Explorer 6?

A. Although this CSS does not include IE6-specific fixes, it does fix the webfonts icon, so it's worthwhile using the conditional code if lt IE 8 rather than if IE 7.
Q. What about Bootstrap 4?

A. I've created a couple of stylesheets for Internet Explorer 8 and 9 to add support for Bootstrap 4. Check it out at: https://github.com/coliff/bootstrap-ie8

The boxsizing.htc polyfill can be a little bit buggy. Please make sure you follow the instructions for using that carefully.