Web and desktop programming, a few common easy questions.

WEB:

Can i make high graphic small games by WEB? I heard it is impossible because of speed problem, but there is client-side programming like Javascript. So is it possible to make high graphic small games using WEB just like it does on desktop?

Can i run, for example, Javascript code in a browser without internet connection?

If web programming can make high graphic games without speed problem, so, why people still learn desktop programming to make small games instead of WEB?

I am learning C# Windows Forms desktop programming over 2 years to make nice games,

did i make a serious mistake?

Should i switch to WEB, for example, ASP.net or Javascript to make pretty good cross platform games?

If you answer these simple question correctly, you help me much, thank you!