What are the browsers and their versions that should be tested to ensure you are testing your sites the best way. Also, do you need to test both on a Mac and PC - iphone, tablet etc.
Is there a good site that will allow you to test your sites on different platforms as well as Mac/PC/iphone…

Thanks for any advice… Gayle

I test on IE 9+, and the current versions of Chrome, Safari, and Firefox. The last three update automatically. So there aren’t a lot of older versions hanging out there. For machines I use an iMac with a Windows VM and an iPad. If the design is responsive, I test on an iPhone. Its good to communicate about what the expectations are for mobile. Some clients will expect performance on their Nokias and Blackberries and others don’t. Also there is a distinction between working on an smartphone and being optimized for an smartphone with swiping actions etc…

Testing of Website is Very Important part of Web Developing , when You are Testing any Site Than you can See number of Issue Collect For Website , Testing is Real Important Part of Developing , I Can Advise For Every User Without Testing you Are not Live Your Site… ???

Yes I understand…testing a website on the browser is very important part. I only test the website on Internet Explores 9 and its latest updates.
If the website support the IE 9 then it must support the other explores as well.

Based on the statistics of usage share of web browsers:
Chrome - 37%
IE - 18%
FireFox 18%
Safari 17%
other web browsers - rest

So Chrome, IE, FireFox and Safari must be tested before launching the website.