What are the most effective and efficient ways to inform( advertise) your audiences to visit an online web site?

Hello, 

In my opinion, if you can't segment among the given population, you can distinguish the product to be informed(or advertised about) from other available products in such a way that it is noticeable.

For Example:  In Facebook we see those lists popping up frequently " top 5 apps you must have for better productivity" or "Things you must do before thinking about buying a branded product:" These type of tagline always catches the users eye and they become interested. 

So let us say the product you think about informing the local population has some features huh can give it a unique and suspenseful punchline such that the viewer is intrigued by it, It is possible to market it online. 

I think this may be a viable option. 

send them the WEB address by email marketing to all the customer we have, to deliver the website to each customer comes to us, typing it in business cards, post it on all the social media, and at last you should add it to google search.

It is is almost impossible, that the whole population is your target audience, i just can't thing of any examples. Even if we take the state law, it is applicable to the whole population but their website cannot target the whole population, there are so many limitations. That is why  when there are new laws or amendments it is not only published in their website, but in news papers, radios and TV channels.

Generally All people may need your services (info on your web) at some time, but All people may not need your service all the time, however some people will need your service all the time.

In my opinion you may have to rethink your target audience and when they will need to visit your website.

The use of content marketing approach, give audience what they like to see or read and you'll draw traffic to your site, hope that helps. 

Thanks

Fully agree with the answer given by colleague Tirthankar