Voting and voting rights can be a tricky issue. Shareholders in small corporations should pay close attention to notices and information received from the corporation, the other shareholders or the directors or officers regarding actions by the corporation or any issues requiring a vote. You should insure that your address and contact information is correct and up to date in the corporation's records for the provision of notice.
As Mr. Doland noted, the requirements for a majority or supermajority vote are typically set out in the bylaws, and you should request a copy of the bylaws from the corporation's secretary. This is true even if there are only two shareholders - while it may seem overly 'formal', even corporations with two shareholders must follow the general rules for all corporations in California, unless they have elected 'close corporation' status which generally permits the corporation to avoid some meeting requirements, etc.
If you believe that there is something afoot by which your rights or interest might be affected, you should: 1) check with the corporation for notices of meetings, etc.; 2) get copies of the corporation's bylaws (and articles); and 3) consult with an attorney regarding any information you receive.
Voting rights are defined int eh Bylaws, and after that the number of shares that actually vote and the majority or supermajority required.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.