Affiliate Marketing Secrets

Hello, I am writing a simple web site. I successfully made the register and log in pages, but now I want to allow only one session per username.
More detailed: When someone logs in a session starts.
If he tries to log in from somewhere else, I want the first session to drop before starting a new session.
How can I do that?
-I already thought of keeping the session ID in the database and change it when the user logs in from another computer. When he tries to go back to the first computer and clicks any link, it checks automatically if the session_id that it has is different compared to the one saved on the database. If it is, it automatically logs out. I could add timed sessions so if the user does not come back to his first computer it automatically closes the session etc.
Problem is that even if I do that, the server will be loaded with sessions that will never be used again until the sessions get timed out. Is there any way to close the session (lets say close a session by knowing its id)?
Any other ideas?

My sister does the virtual school online but we’ve been having problems with her going on Facebook and other stuff and not doing her work. We’re trying to find a program that will block all of that. I downloaded K9 web protection which did a really good job. I thought I could fix it where certain sites were only blocked certain times but I wasn’t able to do that (or I couldn’t figure out how). I heard Net Nanny was good but someone said it didn’t work well on Windows 7.
I really like K9 and will probably stick with it unless I find something with more features so please don’t bother suggesting anything unless it’s capable of blocking only certain sites at certain times like I said. The idea is allowing her access to her school work while blocking Facebook and other things but also completely eliminating a blocker during the weekends and such. The software we have now blocks constantly and can only allow constant access for an hour at a time. It’s a pain to continuously put in a password every hour just to use the computer.
I’ve tried several Chrome and Firefox add-on’s and some were fantastic but could be easily worked around by disabling them or just using another browser.

She’s on the Market
She gaped at it for hours. It appeared too seductive for her to keep her little hazel eyes away. There were many different sizes for it. She always thought the one she had was just right. She was enamored by it’s intellect. It had broadened her mind and disclosed many new notions about the world she lived in. It told her secrets, things her parents and teachers would hide from her because she was young. Everyday it would teach her something new and add to her imagination. Invariably, her parent’s tried to keep her away from it. Luckily, they failed to. Her adoration for it was too dynamic to be broken. Television was her life. It was the love of her life. She knew that she was born part of the media world and nothing could ever change that.
Years have passed now, and this little girl’s passion for media and television has not yet departed. On the contrary, it has only become stronger. She had spent her middle school and high school years taking roles in the Sound of Music and Man of La Mancha. In her junior, she ran a campaign to be senior class president, and won. At an Annual Interstate Speech competition she placed first. Senior year, she was responsible for creating and designer the senior fashion show at her private school. She spent her past summer volunteering at a Senior Health Care, running programs and activities for the elderly. She has recently developed a passion for web designing and has become a freelance web designer.
For the past year or so, she’s has been working in the heart of midtown Manhattan as a Catering Director. Her main responsibilities were targeting major companies in New York City and discussing their catering options. She was in charge of marketing the companies’ food services, trying to make the business grow. In her office, she would sit for hours making cold calls until she nearly ran out of breath. She knew once she had reached a name, or the person in charge of food services, that she had found her target. For days, weeks, and sometimes months she would patiently email the target with follow-ups, advertisements, which she would create on her own, about the companies’ services. After offering discounts, sending complementary lunches, coping with the client’s schedules, she would finally receive an email with a date for the presentation from the company.
She became enlightened by the corporate world. She visited corporate office for companies likes Aeropostale, Michael Kors, Kate Spade, Mac Cosmetics, Diesel, Donna Karan and many more! Not only did she get the wonderful experience of providing the Directors, CEO’S, Marketers, Financial analysts, etc. with presentations but also, she got to work with them. She catered for their needs. She listened to their requests and helped provide satisfactory prices to meet their budgets needs. She created proposals for their events and even catered emergency orders at six in the morning. She developed new marketing tactics and grew a passion for the field. Best of all, she created a good client relationship. Her clients in the media, cosmetics, and fashion industry are what inspired her to follow her dream. When she visited them during fashion week or during holidays to give thanks for their services, they had raised her aspiration. The best part was that she saw that they could work with fashion and advertising at the same time. She dreams of the day she will be able to work in a corporation like those.
So, if you haven’t already heard, she’s on the market. She’s motivated, ambitious, and audacious. There are probably thousands of applicants to choose from for the advertising and marketing communications section at FIT. So, what differentiates her from the rest of the applicants? This girl is ready to use her creativity to bring a new era of advertising and marketing the Media industry. She wants her work displayed and advertised on billboard and in T.V commercials. She wants to work for a fortune 500 companies. She wants to take part in your AMA (American Marketing Association program). She wants to follow her dream. She’s ready to betray her mistress for her career. She’s ready for the competitions of the media world. And she really wants be your next FIT candidate. So what are you waiting for? Products don’t stay on the market forever. Accept her now and you are guaranteed an excellent addition to your school.
*Shipping and handling not included..

1) The feeding relationships among plants and animals and among various animals in a biotic community is called a:
A) biomass.
B) food web.
C) trophic level.
D) niche.
E) symbiosis
2) Which of the following is NOT a consumer?
A) an oak tree
B) a fish
C) a deer
D) a clam
E) an insect

Hi. I joined commission junction and what other site is similar like that where you can pick a lot of different of product/service to promote and make money?