Offer a draw! :P
1.f4!
Why not just wear a sign that says "whip me 'cause I love it!!". If white is going to play that poorly they shouldn't be allowed out in public. As I have stated before, real White players have nothing to fear from the From. Beginners must fear everything however.

black gave a pawn and went for mate.i feel f4 is played after castling.its a double edged sword.u play too early defence is weakened.use it timely it gets u a win.

Well, you certainly can't expect an easy mate, but From's gambit does give black very active piece play and some real positional plusses if accepted. Here is one of my games:

1 f4 d4 Scores -0.20 The idea is to keep white from playing 2.e4 perhaps leaving them with a similar structure to the sicilian (except from whites perspective). Personally I dont like the Bird openingI think it creates a weakess when Short side Castling. The game above illustrates A great H pawn attack further weakening the king side

The most popular response for black from my experience with da Bird is 1.d5 and an early kingside fianchetto (Bg7). From's Gambit 1.e5 can be pretty dangerous. One slip and you're toast. If you are well prepared for From's, and if you don't mind defending for a bit holding onto a pawn in an unclear position, then you might be okay.

I like Birds Opening I play both sides of the line if you play 1.d5 your playing the Dutch defense a tempo down and if you play 1.e5 in response to Birds then you have to be ready for the strong possibility of facing the Kings Gambit 2.e4 a rich tactical mind field!

black gave a pawn and went for mate.i feel f4 is played after castling.its a double edged sword.u play too early defence is weakened.use it timely it gets u a win.
I feel that is the only real truth about f4. If it were otherwise grandmasters would play it more often. BTW- does anyone have a grandmaster game(with rated players, meaning at least 1970's) (non-blitz) that 1.f4 was played??

Not to totally argue with everything everyone has said in here :P BUT... From's gambit is definitely the most ambitious approach to 1. f4. I personally use the From's whenever the opportunity presents itself. The initiative gained for the pawn is consistently enough to get the pawn back with interest (ironically, modern engines, despite being incredibly materialistic, agree with this analysis).

zxb995511 is right as is Anthony
as someone who plays Bird's a lot, From's gambit seems to give black a great advantage, not unbeatable mind you, but it's tricky to emerge as white.

Of course, the From's is far too complex to give any form of concrete proof and it would be unfair to say black has an advantage (being as 1. f4 e5! can simply be met with 2. e4 and a kings gambit position, which can be considered equal or unclear) but in all mainlines black has little trouble gaining the initiative and at least equalizing. That combined with practical results (roughly 40% winning to black) is plenty for me to consider it black's best response.
Using the old russian rule of a pawn being worth 3 tempi, black would actually be considered better. The simple fact that the white knight is forced to move so often (as black develops) followed by trading all those tempo moves into oblivion on g6 (as happens in the mainline) would allow a theoretician to consider black to have full compensation for his pawn with a better position. In practice I believe this is exactly what happens.
if my opponent play 1. f4 .. what do u recommend i play. thanks.