Do you mean by nikah online? i'm sure you can not get married online...erm...i'm so sure of it because you need witness and you have to do the handshake... erm...
but here on some advice from islamonline
Name of Questioner
Rachida - Morocco
Title
Marriage through the Internet: Is it Permissible?
Question
I would like to thank you a lot for the efforts you exert in conveying the message. My question goes as thus: Is it permissible to make marriage announcement on the Internet because we see many people marry via the Internet whether by chat or marriage announcement by sending photos and exchanging ideas? Thanks a lot in advance!
Date
07/Oct/2003
Name of Counsellor
Group of Muftis
Topic
Marriage
Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear sister in Islam, we would like to thank you for showing keenness on knowing the teachings of Islam, and we appreciate the great confidence you repose in us. We hope our efforts meet your expectations.
With regard to your question, Sheikh Hamed Al-Ali, instructor of Islamic Heritage at the Faculty of Education, Kuwait and Imam of Dahiat As-Sabahiyya Mosque, answers:
“This may cause troubles and lead to evil. It is not allowed to put the pictures of Muslim ladies on the Internet for marriage seekers, and it’s also unfathomable to publish the pictures of Muslim ladies and expose their PRIVATE e-mails for everyone to see. Though it’s allowed for the suitor to look at the lady he’s proposing to, this can’t be taken as a proof to legitimize the case at hand, because publishing the pictures online will make the picture sighting general, for the suitor and others. Even the suitor is not allowed to look in this way, as the permissibility of looking at the woman one wants to propose to is based on ghalabat az-Zann or when the acceptance of the lady’s parents has been proved to be near certainty and there is the least amount of doubt concerning it.
This matter needs to be arranged under the supervision of a trustworthy committee, with some pious and honest monitors and they should conduct this matter in top secret. Information about the man and woman should be dealt with as confidential, and picture should be excluded. Then the committee is supposed to tell the man/woman about the suitable person in his/her country or location – without giving the e-mail address or the picture. Then the man should go to propose to the lady and seek permission to look at her or, if he gets some information that the parents are willing and welcoming the idea, can look at her.
Thus, the committee is supposed to do only the first step of helping the man and woman get to know each other. But to allow the man to look at the lady’s picture on the Internet and then start building relationship and leaving the door open to grave consequences to happen is tantamount to spreading evil and corruption among Muslims under the pretext of helping people to get married.”
Shedding more light on the issue, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, says:
“There is nothing wrong, as far as Islam is concerned, in helping people get married through the Internet or any other means. However, I have some reservations regarding using the Internet for that purpose. I know that there are some people who got to know each other through the Internet and this ended in marriage. I myself know some people in our community who got successful marriage through the Internet. However, I have reservation against the way it is carried out.
I would say it is allowed to make marriage announcements on the Internet and provide some information about the man and the lady. But to publish a picture of the lady, even with hijab, is highly undesirable. Though it is permitted for the suitor to look at the woman he is proposing to seek her hand in marriage, publishing her picture on the Internet would expose her to everybody and make it available for people of loose character to use the picture for satisfying their desires. Some people might even use the picture for evil purposes and that would harm the lady in the end. So, caution has to be exercised. We can help people get to know each other, and then they should ask about each other in different ways.
To illustrate, it is not enough for a man to decide to marry a lady through online chatting or some information published on the Internet. That would pose a kind of risk. Marriage is a solemn contract that has to be decided wisely. In choosing one’s partner one has to follow the rules and teachings of Islam in order to have a successful marriage and a prosperous life.”
http://www.islamonline.net/servlet/...h-Ask_Scholar/FatwaE/FatwaE&cid=1119503545044
Assalamo Alaykum brothers and sisters 
