Detect browser version using HTTP headers, add a class to the body tag as well as set a variable.

browser_test.js

            //Check browser version and apply classes to body where applicable
            var body = document.getElementsByTagName('body')[0],
                browserName,
                browserVersion,
                userAgent = navigator.appVersion.toLowerCase();

            if (userAgent.indexOf("msie 8.") !== -1)
            {
                body.classList.add('ie8');
                browserName = 'ie';
                browserVersion = 'ie8';
            }
            if (userAgent.indexOf("msie 9.") !== -1)
            {
                body.classList.add('ie9');
                browserName = 'ie';
                browserVersion = 'ie9';
            }
            if (userAgent.indexOf("msie 10.") !== -1)
            {
                body.classList.add('ie10');
                browserName = 'ie';
                browserVersion = 'ie10';

            }
            if (userAgent.indexOf("rv:11.") !== -1)
            {
                body.classList.add('ie11');
                browserName = 'ie';
                browserVersion = 'ie11';
            }
            if (userAgent.indexOf("edge/12") !== -1)
            {
                body.classList.add('ie12');
                browserName = 'ie';
                browserVersion = 'ie12';
            }