"All is right" 這句子是否正確?

All is right. 這句子絕對正確。

"all" is a pronoun here, representing the whole number or amount (全體, 一切, 全部). Hence, it should take on a singular verb when used as a subject.

Of course, "All is right" is correct and often used.
If you google, you will get many examples such as:
http://www.fisherbabe.com/2011/02/all-is-right-in-lizzyland.html
http://www.therecord.com/sports/local/article/600955--new-facility-new-season-all-is-right-in-synch

2012-01-15 17:18:31 補充：
"is allright或者everything is allright" does not mean exactly the same as "All is right."

1沒有,極少
2正確,意思=everything is right/nothing is wrong.
all(代名詞)is(動詞)right(形容詞,正確)
一般用all(副詞) correct(形容詞)(全對,比如答題),因為越簡越好,不夠簡的自然少人用.
all可以是名詞,代名詞,形容詞,副詞,如果all作形容詞:all apples用眾數.就要用are
002都正確,用alright/all right=好/全對,才1個字,但意思=all is right的省略,所以很多人用:everything is alright/all right(每件事/一切都好/對)都行

通常會用is allright或者everything is allright。