Possession of less than an ounce of marijuana is a misdemeanor punishable by up to a $100 fine (plus "penalty assessments" which are taxes on top of the fine).
Yes, if convicted, you'll have this on your permanent record. There are drug programs available to first time offenders, but you're facing criminal charges so you are entitled to an attorney - either one you hire of if you cannot afford to do so, a public defender.
I respectfully disagree with Mr. Dane. The records of an arrest and/or conviction for Health & Safety Code 11357(b), possesion of less than an ounce of marijuana, must be destroyed two years after the conviction.
Under Health & Safety Code 11361.5(a), "Records of any court of this state, any public or
private agency that provides services upon referral under Section 1000.2 of the Penal Code, or of any state agency pertaining to the arrest or conviction of any person for a violation of subdivision
(b), (c), (d), or (e) of Section 11357 or subdivision (b) of Section 11360, shall not be kept beyond two years from the date of the conviction..."
Section 11361.5(c) says the destruction "shall be accomplished by permanent obliteration of all entries or notations upon the records pertaining to the arrest or conviction, and the record shall be prepared again so that it appears that the arrest or conviction never occurred."
In addition, if you are under 21, a conviction for 11357(b), or almost any other drug- or alcohol-related offense, will result in a one year drivers license suspension.
As a point of clarification -
Yes, Mr. Marshall is absolutely correct - there is a built-in destruction of the records clause associated with simple possession of under an ounce of marijuana.
I probably interpreted the question too literally and assumed they were asking about whether or not an offense such as this with "just a fine" would *ever* appear on their record.
To the original poster - I hope Mr. Marshall's answer helped to clarify and I apologize for any confusion in misreading (or misinterpreting) your question.
And a respectful hat tip to Mr. Marshall.