After I close Firefox tabs, I see code...sometimes 170 pages like this: (function(){var f,aa=aa||{},m=this;function ca(a,b,c){a=a.split(".");c=c||m;a[0]in c||!c.execScript||c.execScript("var "+a[0]);for(var d;a.length&&(d=a.shift())a.length||void 0===b?c[d]?c=c[d]:c=c[d]={}:c[d]=b}function n(a,b){for(var c=a.split("."),d=b||m,e;e=c.shift()if(null!=d[e])d=d[e];else return null;return d}function da(){}function ea(a){a.getInstance=function(){return a.Bm?a.Bm:a.Bm=new a}}

function fa(a){var b=typeof a;if("object"==b)if(a){if(a instanceof Array)return"array";if(a instanceof Object)return b;var c=Object.prototype.toString.call(a);if("[object Window]"==c)return"object";if("[object Array]"==c||"number"==typeof a.length&&"undefined"!=typeof a.splice&&"undefined"!=typeof a.propertyIsEnumerable&&!a.propertyIsEnumerable("s plice"))return"array";if("[object Function]"==c||"undefined"!=typeof a.call&&"undefined"!=typeof a.propertyIsEnumerable&&!a.propertyIsEnumerable("c all"))return"function"}else return"null";

else if("function"==b&&"undefined"==typeof a.call)return"object";return b}function q(a){return void 0!==a}function ga(a){return null!=a}function ha(a){return"array"==fa(a)}function ia(a){var b=fa(a);return"array"==b||"object"==b&&"number"==t ypeof a.length}function r(a){return"string"==typeof a}function ja(a){return"number"==typeof a}function ka(a){return"function"==fa(a)}function la(a){var b=typeof a;return"object"==b&&null!=a||"function"==b}functi on ma(a){return a[na]||(a[na]=++oa)}

var na="closure_uid_"+(1E9*Math.random()>>>0),oa=0;fun ction pa(a,b,c){return a.call.apply(a.bind,arguments)}function qa(a,b,c){if(!a)throw Error();if(2<arguments.length){var d=Array.prototype.slice.call(arguments,2);return function(){var c=Array.prototype.slice.call(arguments);Array.prot otype.unshift.apply(c,d);return a.apply(b,c)}}return function(){return a.apply(b,arguments)}}

function t(a,b,c){t=Function.prototype.bind&&-1!=Function.prototype.bind.toString().indexOf("nat ive code")?pa:qa;return t.apply(null,arguments)}function ra(a,b){var c=Array.prototype.slice.call(arguments,1);return function(){var b=c.slice();b.push.apply(b,arguments);return a.apply(this,b)}}function sa(a,b){for(var c in b)a[c]=b[c]}var u=Date.now||function(){return+new Date};

function ta(a,b){var c=b||{},d;for(d in c){var e=(""+c[d]).replace(/\$/g,"$$$$");a=a.replace(new RegExp("\\{\\$"+d+"\\}","gi"),e)}return a}function w(a,b){function c(){}c.prototype=b.prototype;a.D=b.prototype;a.pro totype=new c;a.prototype.constructor=a;a.QF=function(a,c,g){r eturn b.prototype[c].apply(a,Array.prototype.slice.call(arguments,2))} }

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etc., etc.

There are no tabs open. just a window of firefox with all this code in it. I have no idea what this is.
My thought it has something to do with windows, as it seems to happen after updating windows 7, sp1...if I recall. I don't know what sites I may have been looking at at the time...didn't write those down (will next time if it happens again.) So far it's happened around 4 times since the beginning of the year.
Several Questions arise: What is it? What does it do? Is my computer compromised? Is my computer secure? Should I worry about it? or is it just another annoyance of Firefox and Windows combined?