From a consumer’s point of view, I think the most common mistakes online marketers make is spamming people with mails. It is crippling, and it needs to stop. Take for example, I am expecting some very important mail, and i got notified of a new mail, and while rushing to check, I realised it is a mail from those online stores, I’d be so pissed that I wouldn’t even bother to read the mail nor check if i actually need those products. In extreme cases, I can unsubscribe from their mailing list. Spamming does not translate to huge sales please, it is disturbing. schedule your mailing and make it brief and catchy.