Periods longer than 6 months can reset the residency requirement. And have to be resident for 18 months out of 3 years when married to a US Citizen.

You can find out more here: http://www.uscis.gov/files/article/M-476.pdf

Ok, now if i understood, that i cant leave the country for 18 months, out of 3 years.
which that means i have to stay after i became a resident 18 months in the usa?? or i still can travel and back to usa but within 3 years i have to live here in the usa 18 months, and not necessary to be on 1 time? correct?

Ok Again lol, do u mean 6 months for all this 3 years ?? or no more than 6 months each trip ?

Ok Again lol, do u mean 6 months for all this 3 years ?? or no more than 6 months each trip ?

If you are at least 18 years old and:
Are currently married to and living with a U.S. citizen;
and Have been married to and living with that same U.S.
citizen for the past 3 years;
and Your spouse has been a U.S. citizen for the past 3 years.
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Time as Permanent Resident: 3 Years
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Continuous Residence: 3 years as a Permanent Resident without leaving the
United States for trips of 6 months or longer.
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Physical Presence in the United States: 18 Months
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Time in USCIS District or State: 3 Months
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For the three year period preceeding submitting your N-400:

*No single trip should exceed 6 months.

*The combined total of your trips should not exceed 18 months.

Also, after you have submitted your N-400, but before it is completed, be aware that the "requirements" remain.

Hope that is clear to you.