i got this new yamaha. and its a pretty good guitar except that theres a fret buzz only on two first strings. specially on the chord F. and would getting lighter strings help the problem? if so what kind of strings would i get?

You came to the right place for help.  The people on this site have helped me TONS.  What I've been able to gather from them is that you need to have your setup checked and possibly reset for your style of play.

Anyway, welcome to the forum.  I think you'll enjoy the people here as well as their help.

Dean

Good question , wat kind of strings did it come with,did you get it new,has it ever been setup ,so many factors to look at in that area,but if it came with light strings then you should keep using lights because thats what its set for.Although most ive seen come with medium strings unless they are beginner guitars then they may have lights, My suggestion is decicde what thickness of string you want then go get a setup that should fix your problem and it sure want hurt it.......O and welcome aboard hope you enjoy your stay....

pretty much you gotta have your guitar setup by a pro especially if you havent done your own guitar work before.

basically you are fretting out, which means that the string is touching the fret when it vibrates creating the "buzz".

the solution is usually one of two things:

adjusting the "action" (or string height) at the saddles (where the string meets the bridge).
       this one you can play around with a little without doing any real damage.

adjusting the neck bow/curve with the truss rod.
       I HIGHLY RECOMMEND AGAINST MESSING WITH YOUR TRUSS ROD. it can permanently damage the neck of your guitar if you dont know what you are doing.

in your case, i would suggest getting your guitar setup by a pro. my local shop did a pup replace, fret board oil, set my intonation, set my action, and did a string replace for about 50 bucks. so you can prob get it done for less than that and it can definately be a pain to play with fret buzz.

so frets maybe third or fourth might be a little higher than should be... had it on my squire

All you need to do is scoop the mids.

In all seriousness; while it depends on what kind of guitar it is and the style you're playing, some amount of fret buzz is acceptable. The key is whether or not you can tell it's there through the amp (if you're using one).

If it's an electric check how close your pickups are to the strings. That one threw me off for a while on a guitar. I thought the board was tweaked or something but it turned out the neck pickup was pulling the strings down just enough for fret buzz to show up at times.

As far as strings go, everyone is right in that you ideally want to stay with the same gauge of strings. Brand matters less, but your intonation will be affected if you change string gauges.

That said, intonation as it applies to strings is a function of gauge. More specifically the wound strings will be dependent on the size of the core. Usually the cores are the same (or close enough to not be noticeable) between brands. Different alloys do result in different tensions and varying vibration patterns that can affect fret buzz.

If you know what brand and type of strings you're playing someone here should be able to figure out a similar set with higher tension to try.