Testing your website in different browsers- Cross browser compatibility

There are many services available on the internet which will let you know how you website/ webpage will appear on different browser or different version of same browser or same browser in different Operating systems. I tried looking for some free services for a project. Two services that look good

http://browsershots.org/

Pros- FREE, supports 100+ combination of browser and OS, No Registration required- you are good to go by just providing site link

Cons- Slow, incomplete results for some cases

https://browserlab.adobe.com/

Pros- Free, Fast, Chose browser at runtime and change

Cons- Limited browser selection, Registration required, Did not work for some of the mentioned browsers(may be temporary issue)