Textual Ad or Display Ads, which works best for an Digital Product?

If you have an ebook that you can sell. Where would you put it?

Please Tell me Differentiate between on-page and off-page optimisation ?

Competitors are building bad links for me. Links from unnatural sources. What should I do?

As I am reviewing one of my site's metrics I see that the site is getting pretty much good direct traffic. In fact 90% of its traffic is direct and they are getting conversions too. But we haven't promoted the site in any way. So, how come the direct traffic is coming? And is it going to hurt my site?

Do you think that Outbrain is better than taboola?

How do you recover from Writer's Block?

Are there any good books for A/B Testing? Where I can learn how to perform A/B testing from scratch.

I am looking for a paid solution to Google Keyword planner. SEMrush is good but its a bit pricey. So, can anybody suggest any good alternative to them in low price.

Why my most of the mails are going to spam folder? I don't understand. Most of the subscribers of my list are gmail users. So, I was just wondering, is this something has to do with gmails?