I've been in the business of online training for almost 9 years now and have seen a dramatic change in attitude towards online Certification. More and more schools around the world recognize the value of online certificates issued by professional organizations and employers no longer discriminate between Certificates obtained through traditional institutes and those online. Just be careful who you choose as your course provider (and this applies whether they are online or not) and make sure what they offer is of good standard.
Just to reset the balance in this discussion on onsite vs online, as it were

here are some of the advantages online courses offer.
• Online courses offer a great training opportunity at entry level. They can provide a thorough grounding in a new career and the right tools to approach a new profession within a manageable amount of time and finances.
• Online courses offer a convenient way to test the water and allow you to see if teaching is indeed for you. People’s motivations to become a teacher are manifolds. What often happens is that of those who trained, some will find after a couple of years’ teaching that they don't like it at all and will move into an entirely new direction, whilst others will stay with the profession and go on to a Diploma course and further professional development.
• Online courses allow you to study while holding onto your daytime job or taking care of your family, or fulfilling prior study commitments. An online student can usually take the course any time during the day or week, so essay writing and researching assignments for example can be carried out whenever it suits you.
• Online courses allow you to correspond with qualified teacher trainers from wherever you are in the world. Even if you are in a remote area of the planet, as long as you have an Internet connection you can have access to top teacher trainers and benefit from their knowledge and experience.
• Online courses allow you to choose your personal tutor. How many traditional courses have more than one or two teacher trainers available at any one time? And how many will allow you to switch onto another tutor if you are not happy with your current one?
• Online courses give flexibility. Many students work on their course during the middle of the night or early in the morning. The flexibility of the course makes it possible for them to complete their course, while attending in house courses might be impossible due to their work schedules.
• Online courses are very affordable and can be undertaken without breaking the bank. Working online allows online course providers to cut down considerably on overheads. This saving can then be passed on to their students resulting in low course fees.
• Online courses allow one-on-one interaction with your personal tutor 24/7. The Internet makes it possible for you to ask questions and receive the answer back almost immediately.