No Download Blackjack
There are many that worry about downloading software to their computers not only just incase there is a virus but mainly will it work on your machine? Maybe your using a family members machine and they don't want you to install anything etc... what ever the reason there is no reason why you can't play blackjack online. Many online casinos have instant play live on their site that doesn't require any download, instant play casinos normally use flash which is widely available on most machines and used by many sites.
Flash support has been dropped from most mobile devices though so for this there is HTML 5 versions of casinos, like flash this also doesn't require any download, all you need is an up to date web browser that supports the latest HTML 5 technology.