Adobe BrowserLab
Adobe BrowserLab is an amazing tool. I have used this tool so much when it comes to testing a website. It has every major browser AND lets you set up a custom list of browsers you want to test in. It even gives you the option to onion skin the displays between browser so you can easily compare what’s different in each browser. This tool is free to use as long as you have an Adobe account, which is free to create. It’s all web based, so you can use it anywhere without downloading anything. The only downside of BrowserLab is that it renders the website to an image, so you cannot test functionality. You can learn more about this great tool here.