Ghostlab offers synchronized testing for scrolls, clicks, reloads and form input across all your connected devices, meaning you can test the entire user experience, not just a simple page. Using the superior built-in inspector, you can discover and fix problems quickly, connected to the DOM or JavaScript output on any device.

Ghostlab is available for both Windows and Mac OS X, with no setup required, as it can instantly connect to any JavaScript-enabled client. Using the Ghostlab server, you can sync pages from your local directory, your localhost Apache setup or any server in the world, with automatic reloading to keep track of file changes. The workspace feature lets you create a custom browser setup, and adapt Ghostlab's features to exactly what you require.

Price: $49

BrowserStack provides live, web-based browser testing with instant access to every desktop and mobile browser (currently more than 300), with the ability to test local and internal servers, providing a secure setup. The cloud-based access means no installation is required, and the pre-installed developer tools (including Firebug Lite, Microsoft Script Debugger and many more) are useful for quick cross-browser testing and debugging.

The official iOS, Android and Opera mobile and tablet emulators help you test across a huge range of devices. Using the BrowserStack infrastructure, you can quickly setup a comprehensive testing environment with support for firewalls, proxies and Active Directory.

Price: $39 per month (Solo) - $399 per month (Enterprise)

Sauce Labs allows you to run tests in the cloud on more than 260 different browser platforms and devices, providing a comprehensive test infrastructure including Selenium, JavaScript, Mobile and Manual testing facilities. There's no VM setup or maintenance required, with access to live breakpoints while the tests are running so you can jump in and take control to investigate a problem manually.

Sauce Labs lists your recently run tests chronologically, with info about the testing platform, runtime, build and whether they passed or failed. Once a test is complete, you'll receive a full report with the metadata and log files, and you can flip through screenshots to diagnose errors and verify layouts, or even watch a screencast of the whole test.

Price: $12 per month (Manual) - $149 per month (Small Team)

CrossBrowserTesting offers a live testing environment with access to more than 130 browsers across 25 different operating systems and mobile devices, so you can interactively verify your layout and test AJAX, HTML Forms, JavaScript and Flash.

The impressive layout comparison feature lets you choose a "base" browser for comparisons and get a summary of rendering differences, along with a screenshot of side-by-side images to catch and debug layout issues effectively. You can test local development of websites even behind firewalls and logins, with the ability to change browser, cache and cookie settings, and turn JavaScript on or off.

Price: $29.95 per month (Basic) - $199.95 per month (Business)

Browsershots is a free, open-source web app providing a convenient way to test your website's browser compatibility in one place. Browsershots uniquely champions the idea of distributing the work of making screenshots among community members, who set up "factories" on their own machines, to get jobs from the server using a fully automatic unattended script.

It's simple to use -- simply enter the URL and choose the browser setup you require. There are several presets to choose from, including screen size, color depth, JavaScript, Java and Flash. You will then have to wait a specified period of time until your request is processed. When the screenshots are ready, they'll appear, and you can bookmark your processing page to come back to it later.

Price: Free - $29.95 per month (Priority Processing)

Browserling, built upon StackVM and powered entire by Canvas and JavaScript, lets you run fully interactive browser testing sessions without Flash, Applets or anything to install. Once you enter the URL you want to test, you wait until the test is ready, you then have three minutes to review your site in multiple browsers.

There are more than 80 browser combinations to choose from, along with the ability to change the screen resolution. Once your time is up, you'll be asked to re-submit your URL or upgrade to a paid plan, which includes SSH tunnels to access localhost and Intranet services, remote desktop access and higher time limits to test as much as you need.

Price: Free - $250 per month (Dedicated)

Browsera tests cross-browser layout problems by automatically comparing each browser's output and locating and reporting JavaScript errors. You can test pages behind logins, as Browsera can handle logging in prior to running each test, with no installation required (the service runs entirely in the cloud).

Instead of testing single pages, you can test your entire site by crawling the links on your site or accepting a list of URLs you'd like to test. There's support for dynamic content such as AJAX and DHTML, since Browsera waits until the page has finished loading before testing. You're alerted to issues quickly, as possible cross-browser layout problems are immediately flagged and presented.

Price: Free - $99 per month (Premium)

Mogotest visually analyzes your website or app to help you ship better products, providing cross-browser compatibility reports to see in which browsers your pages may appear broken, and drill down for more information. There's no programming knowledge required; just enter a set or URLs and the results are delivered quickly.

You can securely test pages located behind a login or firewall, with a site health report that ensures your live site is configured properly. The screenshot comparison tool is especially helpful, with which you can see how two browsers look in relation to one another -- essential for pixel perfect work. The regression testing also means you never have to worry about whether making a CSS or JavaScript change will break your page.

Price: $99 per month (Professional) - $499 per month (Premium)

IE NetRenderer allows you to check how your website performs in Internet Explorer 5.5 through 11. Just type in your URL and see how your website appears in common IE versions. Once rendered, you can choose between nine versions of IE, and you're presented with the processing time of the request and the dimensions of your website design.

IE NetRenderer is able to process a large number of requests in parallel and in real time, so it's an incredibly fast service, with no waiting time. A unique Mixed Overlay and Difference Mode helps to identify subtle positioning differences between IE6 and IE7. All rendered images and URLs are kept private and secure.

Price: Free

Litmus offers one-stop email and cross-browser testing. Once you enter your URL, Litmus will show how it appears in the most popular web browsers. Link validation means you can verify all of your links and also make sure the URLs you're linking to aren't blacklisted. The flexible setup allows you to add team members, clients and partners to a testing project, without limits on users or tests and unlimited access to all the features available.

If you're a Mac OS X user, you have the added advantage of using Alkaline, a free Mac app to run email and browser tests right from your desktop. With a range of plugins, Alkaline lets you test page designs across multiple browsers without dealing with virtual machines.

Price: $79 per month (Basic) - $399 per month (Premium)

BrowseEmAll helps you find cross-browser issues quickly, optimize your site for mobile devices, test local pages and even run different browsers side-by-side for layout comparison. There's support for all major browsers, with BrowseEmAll keeping track of new browser releases and updates. The simulators for iOS and Android allow you to scroll, zoom and interact as if you were on the real device, and switch between landscape and portrait mode.

BrowseEmAll runs on your local machine, so you can easily test websites protected by a firewall, and create detailed cross-browser reports with browser specific and full-page screenshots. You can run up to four different browsers side-by-side and quickly see how a change affects the rendering in your chosen browsers.

Price: $69 (Standard License) - $349 (Team License Package)

TestingBot provides easy cross-browser testing with Selenium, either manually or automated, with more than 100 browser and OS combinations. The live, manual testing allows you to control any browser in the cloud interactively from your own browser. You can run automated tests in the cloud by specifying which browsers you want to test, when the test should run and for how long.

Each browser test features advanced reporting, multiple screenshots and even a video of your test, to verify the test has run correctly and, if a test fails, to check why. A secure testing environment allows you to run tests on your local computer, on a LAN or on a server via VPN.

Price: $40 per month (Small Team) - $250 per month (Custom)

Spoon.net is a browser sandbox (currently Windows-only) to test or deploy multiple versions of current, beta or legacy web browsers without maintaining cumbersome virtual machines. Just log in, install a small plugin, select the browser you want to test and it will launch instantly. Because Spoon.net runs the applications in isolated "sandboxes," you can run multiple applications side-by-side without any conflicts or dependencies.

The virtual browsers behave exactly like installed browsers, with support for standard browser components such as Java, ActiveX and popular plugins like Firebug, IE Developer Toolbar, and CSS and JavaScript debugging consoles.

Price: Free - $99 per month (Team)