I think that these are top 10 certification in Internet Marketing. 1. Marketing Principels and Practices 2. Marketing Rearch 3. Internet Market Research 4. Marketing communication Writing 5. Building the Brand Experience 6. Advertising Copywriting 7. Event Marketing 8. Global Marketing 9. Brand Management Marketing 10. Social Media Marketing
I think the most reputable one is Google Adwords certifications plus you get to enter Google's advertisers database.
Certification would be really good, but not entirely necessary. You could try I think it's called Phoenix university online or somethin like that, they have a bachelor's degree in i.m. Good luck!