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ummm ok?

White's best is 5.c3, when Black can be greedy (dangerous) or play safely 5...Nf6, which transposes to the old Italian game. This is regarded today (against FIDE Master Herve Daurelle) as completely equal. Here is a game I finished recently at correspondence chess, which was inevitably drawn- factly none of the players have played a move of their own in this game!

5.0-0 Nf6 6.e5 is the murky Max Lange attack, but Black can play the safer 5...d6 6.c3 Bg4! when he is slightly better.

If the question is, what should white play in this position? I'm pretty sure there are 3 alternatives; o-o, c3, or Ng5. I don't play the scotch as white but I face it a lot as black. 

5.Ng5 is not a good move, e.g. 5...Nh6 6.Nxf7 (on 6.Qh5 both Qf6 and Qe7 are perfectly adequate) Nxf7 7.Bxf7+ Kxf7 8.Qh5+ g6 9.Qxc5 d6, and Black has the advantage due to his good central control and slight development preponderance (his king is perfectly safe).

i play N g5

this is the link of thr group of scotch gambit for all informations 

http://www.chess.com/groups/home/scotch-gambiteers

Yes pfren, I play this exact line as black against Ng5 (including 9...d6) but I do know that in some databases 9...d5 is more popular. They might play equally as good for black but d6 looks like the safer move to me.

this was the 1st aggressive open line I ever harnessed. 1 of my favorites is the classic line where after 5.c3 5...dxc3 6.Bx7!?

and then of course refusing to catch on c3 until they take on b2 and recapture with the B is always a fun game. ahh...the good ole days..

A matter of taste, really. 9...d5 is IMHO a tad less accurate because of 10.0-0! fe4 11.c3, when white is only marginally worse.

I prefer keeping the advantageous (for Black) pawn stucture impact, so for me 9...d6 is the best move, but I won't argue that 9...d5 is also good for a (slight) advantage.

@CheesyPita, as well as answering the OP question, it is a very interesting position: after 6 Nxc3, the alternative to 6 Bxf7+

It's a tactical line with good chances for white, and probably full compensation for the pawn.

EDIT: Pfren, how is the line I posted irrelevant?

The line is touched upon here:

http://www.chesscafe.com/text/kibitz75.pdf

Of 6 Bxf7+ line it says, "6 Bxf7+ is the obvious shot, it is usually recommended and is safe but I am unsure whether White gains a really significant advantage against best defence."

Of 6 Nxc3: "It seems that 6 Nxc3 is a risky move for White, although the potential pay-off is Black goes wrong is greater than with 6 Bxf7+."

It is generally conceded that 6 Bxf7+ is objectively stronger and allows white to kep a safe advantage in all lines, but 6 Nxc3 has its merits as well. I think you put things too simply.

You could (at the very least) do a little work before posting irrelevant stuff. 5...dc3 is not good because of the pretty typical 6.Bxf7+, when white keps a safe advantage in all lines.

Don't be so grumpy, granpa pfren! birdsopening is obviously not an opening expert...

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That was my impression.