Unlike Firefox, Opera, Chrome etc, it is not easy to run multiple versions of Internet Explorer side-by-side.
It gets especially difficult since Internet Explorer 6 to 9 are only supported are not all supported on all versions of Windows. Internet Explorer 6 is only supported on Windows XP, and can not be installed on Vista, or 7; Internet Explorer 7 is only supported on Windows XP, and Vista; Internet Explorer 8 is the only one supported on all, and then Internet Explorer 9 drops support for XP. If you want to test the upcoming Internet Explorer 10, you will need Windows 7. So just to test you website across all version of Internet Explorer, you would normally need licences for two versions of Windows XP, and 7.
This is where IETester steps neatly in. As its name suggests, it is an application that makes it easy to test your website on different versions of Internet Explorer. Through one single interface, you can see how any web page looks in multiple versions of Internet Explorer. It supports even the latest Internet Explorer 10 and goes all the way back to Internet Explorer 5.5 with all versions in between.
Each engine can be loaded in a separate tab so the same page can be tested on multiple versions at the same time. In fact if you set a home page, it will open by default on each browser if you open it in a tab.
Testing a web page on all browsers is as simple clicking on the “All IE versions” button on the Home tab of the Ribbon bar — yes, IETester uses a Ribbon UI. This shows a dialog box where one can enter the URL of the page that needs to be tested, select the browsers you wish to test the page on, and click OK. Optionally, you can pick an HTML file from your computer.
There are a couple of interesting features that IETester supports that can make testing websites even easier. It is possible to get a split-screen view, with two different browser versions side-by-side, or horizontally above each other. To do this you can simply drag a tab to the left edge, or the bottom edge, and the there will be an indication that the tab will attach there. Another amazing features that simplifies testing is a support for the multi-process model. This is optional, however it means that one of the browser tabs can crash without crashing the app itself.
IETester is a free download, and works on Windows XP, Vista and 7. It includes all supported Internet Explorer versions except 10, which you need to install separately and copy some files since it is still pre-release. You can download IETester from here.