jquery version of pushup: http://www.pushuptheweb.com/

pushup.js

/* Pushup
 * Copyright (c) 2008 Nick Stakenburg (www.nickstakenburg.com)
 *
 * License: MIT-style license.
 * Website: http://www.pushuptheweb.com
 *
 */

var Pushup = {
	Version: '1.0.0.1.jquery',
	options: {
		appearDelay: .5,
		fadeDelay: 6,
		images: '../images/pushup/',
		message: 'Important browser update available',
		reminder: {
			hours: 6,
			message: 'Remind me again in #{hours}'
		},
		skip: true
	},
	updateLinks: {
		IE: 'http://www.microsoft.com/windows/downloads/ie/',
		Firefox: 'http://www.getfirefox.com/',
		Safari: 'http://www.apple.com/safari/download/',
		Opera: 'http://www.opera.com/download/'
	},
	Browser: {
		IE: $.browser.msie,
		Firefox: $.browser.mozilla,
		Safari: $.browser.safari,
		Opera: $.browser.opera
	},
	MinVersions: {
		IE: 7,
		Firefox: 2,
		Mozilla: 1.9,	// Firefox 3.0
		Safari: 500,
		Opera: 9.25
	}
};

Pushup.conditions = {
	IE: Pushup.Browser.IE && 
		$.browser.version < Pushup.MinVersions.IE,
	Firefox: Pushup.Browser.Firefox &&
		parseFloat($.browser.version) < Pushup.MinVersions.Mozilla,
	Safari: Pushup.Browser.Safari &&
		$.browser.version < Pushup.MinVersions.Safari,
	Opera: Pushup.Browser.Opera && 
		$.browser.version < Pushup.MinVersions.Opera
};

(function() {
	// find current browser and check if it needs an update
	for (var browser in Pushup.Browser)
		Pushup._browserUsed = (Pushup.Browser[browser]) ? browser : Pushup._browserUsed;
	Pushup._updateBrowser = Pushup.conditions[Pushup._browserUsed] && Pushup._browserUsed;

	// stop if no update is required and we want to skip build
	if (!Pushup._updateBrowser && Pushup.options.skip) return;

	function Extend(destination, source) {
		for (var property in source)
			destination[property] = source[property];
		return destination;
	}

	Extend(Pushup, {
		start: function() {
			// get the image directory
			if (this.options.images.indexOf('://') > -1)
				this.images = this.options.images;
			else {
				var srcMatch = /pushup(?:-[\w\d.]+)?\.js(.*)/,
					scripts = document.getElementsByTagName('script');
				for (var i = 0, l = scripts.length; i < l; i++) {
					var s = scripts[i];
					if (s.src && s.src.match(srcMatch))
						this.images = s.src.replace(srcMatch, '') + this.options.images;
				}
			}
			if (Pushup._updateBrowser) this.show();
		},

		build: function() {
			this.$pushup = $('<div />');
			this.$pushup.addClass('Pushup').addClass('withoutReminder').attr('id', 'pushup');
			this.pushup = this.$pushup[0];
			Opacity.set(this.pushup, 0);

			this.$messageLink = $('<a />');
			this.$messageLink.appendTo(this.pushup).addClass('pushup_messageLink').attr('target', '_blank');
			this.messageLink = this.$messageLink[0];

			this.$icon = $('<div />');
			this.$icon.appendTo(this.messageLink).addClass('pushup_icon');
			this.icon = this.$icon[0];

			this.$message = $('<div />');
			this.$message.appendTo(this.messageLink).addClass('pushup_message').html(this.options.message);
			this.message = this.$message[0];

			// reminder message if cookies are enabled
			var hours = this.options.reminder.hours;
			if (hours && Pushup.cookiesEnabled) {
				var H = hours + ' hour' + (hours > 1 ? 's' : ''),
					message = this.options.reminder.message.replace('#{hours}', H);
				this.$reminder = $('<a />');
				this.$reminder.appendTo(this.pushup).attr('href','#').addClass('pushup_reminder').html(message);
				this.$pushup.removeClass('withoutReminder').addClass('withReminder');
			}

			// Older Opera doesn't handle float correctly
			if (Pushup.conditions.Opera) {
				this.$messageLink.css('float', 'none');
				this.$reminder.css('float', 'none');
			}

			Pushup.setBrowser(Pushup._updateBrowser);
			$(body).append(this.pushup);
			Pushup.addEvents();
		},

		addEvents: function() {
			if (this.$reminder) {
				this.$reminder.click(function(event) {
					Pushup.setReminder(Pushup.options.reminder.hours);
					Pushup.fade();
					return false;
				});
			}
			this.$pushup.mouseover(function() {
				Pushup.clearFade();
			}).mouseout(function() {
				Pushup.fade({ delay: Pushup.options.fadeDelay })
			});
		},

		setBrowser: function(browser) {
			browser = browser || 'IE';
			setPngBackground(this.icon, this.images + browser.toLowerCase() + '.png');
			this.messageLink.href = this.updateLinks[browser];
		},

		show: function() {
			// default to IE if no browser was detected
			var browser = typeof arguments[0] == 'string' ?
				arguments[0] : Pushup._browserUsed || 'IE',
			 options = arguments[browser ? 1 : 0] || {};

			if (options.resetReminder) Pushup.resetReminder();

			// show if not blocked by cookie
			if (!options.ignoreReminder && Pushup.cookiesEnabled &&
				Cookie.get('_pushupBlocked')) return;

			if (!Pushup.pushup) Pushup.build();
			Opacity.set(Pushup.pushup, 0);
			Pushup.pushup.style.display = 'block';
			if (browser) Pushup.setBrowser(browser);
			this.appear({ fadeAfter: true, delay: Pushup.options.appearDelay });
		},

		appear: function(delay) {
			Pushup.clearFade();
			var options = arguments[0] || {};
			return window.setTimeout(function() {
				Appear(Pushup.pushup, { afterFinish: function() {
					if (options.fadeAfter)
						Pushup.fade({ delay: Pushup.options.fadeDelay });
					}
				});
			}, (options.delay || 0.01) * 1000);
		},

		clearFade: function() {
			if (Pushup._fadeTimer) {
				window.clearTimeout(Pushup._fadeTimer);
				Pushup._fadeTimer = null;
			}
		},

		fade: function() {
			var options = arguments[0] || {};
			Pushup._fadeTimer = window.setTimeout(function() {
				Fade(Pushup.pushup);
			}, (options.delay || 0.01) * 1000);
		},

		setReminder: function(hours) {
			Cookie.set('_pushupBlocked', 'blocked', { duration: 1 / 24 * hours })
		},

		resetReminder: function() { Cookie.remove('_pushupBlocked') }
	});

	// Opacity adapted from the Prototype JavaScript framework
	// http://www.prototypejs.org
	var Opacity = {
		set: function(element, value) {
			element.style.opacity = (value == 1 || value === '') ? '' : ((value < 0.00001) ? 0 : value);
		},

		get: function(element) {
			var opacity = element.style.opacity;
			return opacity ? parseFloat(opacity) : 1.0;
		}
	};

	if (Pushup.Browser.IE) {
		Opacity.get = function(element) {
			var opacity = element.style.opacity;
			if (!opacity && element.currentStyle) opacity = element.currentStyle[opacity];

			if (opacity = (element.style.filter || '').match(/alpha\(opacity=(.*)\)/))
				if (opacity[1]) return parseFloat(opacity[1]) / 100;
			return 1.0;
		};

		Opacity.set = function(element, value) {
			function stripAlpha(filter) {
				return filter.replace(/alpha\([^\)]*\)/gi, '')
			}
			var currentStyle = element.currentStyle;
			if ((currentStyle && !currentStyle.hasLayout) || (!currentStyle && element.style.zoom == 'normal'))
				element.style.zoom = 1;
			var filter = element.style.filter,
				style = element.style;
			if (value == 1 || value === '')
				(filter = stripAlpha(filter)) ? style.filter = filter : style.filter = '';
			else 
				style.filter = stripAlpha(filter) + 'alpha(opacity=' + (value * 100) + ')';
		};
	}

	function Appear(element) {
		var current = Opacity.get(element),
			options = arguments[1] || {};
		if (element.style.display != 'block')
			element.style.display = 'block';
		if (current < 1) {
			setTimeout(function() {
				Opacity.set(element, current += 0.05);
				Appear(element, options);
			}, 0.01);
		}
		else {
			if (Pushup.Browser.IE && element.style.filter)
				element.style.removeAttribute('filter');
			if (options.afterFinish) options.afterFinish.call();
		}
	}

	function Fade(element) {
		var current = Opacity.get(element),
			options = arguments[1] || {};
		if (current > 0) {
			setTimeout(function() {
				Opacity.set(element, current -= 0.05);
				Fade(element, options);
			}, 0.01);
		}
		else {
			$(element).hide();
			if (options.afterFinish) options.afterFinish.call();
		}
	}

	function setPngBackground(element, url) {
		var options = Extend({
			align: 'top left',
			repeat: 'no-repeat',
			sizingMethod: 'crop',
			backgroundColor: ''
		}, arguments[2] || {});

		Extend(element.style, arguments.callee.IEBelow7 ? {
			filter: 'progid:DXImageTransform.Microsoft.AlphaImageLoader(src=\'' +
				url + '\'\', sizingMethod=\'' + options.sizingMethod + '\')'
		} : {
			background: options.backgroundColor + ' url(' + url + ') ' +
				options.align + ' ' + options.repeat
		});
	}
	setPngBackground.IEBelow7 = Pushup.Browser.IE && $.browser.version < 7;

	// Based on the work of Peter-Paul Koch - http://www.quirksmode.org
	var Cookie = {
		set: function(name, value) {
			var expires = '', options = arguments[2] || {};
			if (options.duration) {
				var date = new Date();
				date.setTime(date.getTime() + options.duration * 1000 * 60 * 60 * 24);
				value += '; expires=' + date.toGMTString();
			}
			document.cookie = name + "=" + value + expires + "; path=/";
		},

		remove: function(name) { this.set(name, '', -1); },

		get: function(name) {
			var cookies = document.cookie.split(';'), nameEQ = name + "=";
			for (var i = 0, l = cookies.length; i < l; i++) {
				var c = cookies[i];
				while (c.charAt(0) == ' ')
					c = c.substring(1,c.length);
				if (c.indexOf(nameEQ) == 0)
					return c.substring(nameEQ.length, c.length);
			}
			return null;
		}
	};

	// check if cookies are enabled
	Pushup.cookiesEnabled = (function(test) {
		if (Cookie.get(test)) return true;
			Cookie.set(test, 'test', { duration: 15 });
		return Cookie.get(test);
	})('_pushupCookiesEnabled');

	$(document).ready(function() { Pushup.start(); });
})();