Change Browsers Favicon Dinamically using JavaScript (Credits: http://softwareas.com/dynamic-favicons/)

dynamic-favicon.js

var favicon = {
    change: function(iconURL) {
        if (arguments.length == 2) {
            document.title = optionalDocTitle
        }
        this.addLink(iconURL, "icon")
        this.addLink(iconURL, "shortcut icon")

        // Google Chrome HACK - whenever an IFrame changes location 
        // (even to about:blank), it updates the favicon for some reason
        // It doesn't work on Safari at all though :-(
        if (!IE) { // Disable the IE "click" sound
            if (!window.__IFrame) {
                __IFrame = document.createElement('iframe')
                var s = __IFrame.style
                s.height = s.width = s.left = s.top = s.border = 0
                s.position = 'absolute'
                s.visibility = 'hidden'
                document.body.appendChild(__IFrame)
            }
            __IFrame.src = 'about:blank'
        }
    },

    addLink: function(iconURL, relValue) {
        var link = document.createElement("link")
        link.type = "image/x-icon"
        link.rel = relValue
        link.href = iconURL
        this.removeLinkIfExists(relValue)
        this.docHead.appendChild(link)
    },

    removeLinkIfExists: function(relValue) {
        var links = this.docHead.getElementsByTagName("link");
        for (var i = 0; i < links.length; i++) {
            var link = links[i]
            if (link.type == "image/x-icon" && link.rel == relValue) {
                this.docHead.removeChild(link)
                return
            }
        }
    }, // Assuming only one match at most.

    docHead: document.getElementsByTagName("head")[0]
}