Many search engines have ways of knowing if a link is visible or not. Such websites can also be penalised by those search engines in terms of ranking, so your clients will be unduly punished.
Just be honest. Request to the client that the link is there, or just don’t put it. If they find that you’ve put it there after they’ve explicitly asked you to, then you will lose all trust from them, preventing future business.
Google for “backlink” and the first site in the list is Wikipedia.
The snippet starts off “Backlinks are incoming links to a website or web page.”
A backlink is a link back to your website from some other website.
If you persuade another web author to put a link to your site on his site, and then hide the link with CSS, then:
(1) you lose the opportunity for actual people to follow the link and find your site, and
(2) Google will assume it is spam or a link farm or some other such undesirable site, and at best will ignore your site and his, and at worst will blacklist and block them.
What you seem to be describing is a “back to top” link. These have no effect on SEO at all, but if you have long pages with lots of text, they might be useful for people reading your site … but only if they are visible, not if they are hidden!
I’m assuming you’re saying that because the link had a hash character rather than a URL? I just thought he did that to save time typing out a made up URL.
I agree with Jake, hiding links back to your site on a client site is both unethical and pointless and could even hurt them if Google decide to penalise them for using spammy SEO techniques. Not good at ll, don’t do it. I always ask my clients for their permission to add a ‘referral link’ to their site and I always get one.
Yes, that was how I interpreted it but I can see that it might not have been right.
Either way, I stand by the point that hiding links to your site is likely to damage both your site and the other site’s reputations with Google, and it reduces the number of people who will find your site by following the links. Either make it a visible link or survive without it.
Like others said, search engines can recognize if you hiding your links in divs. There used to be a lot of black hat SEO techniques such as making link text the same as the background colour to hide from human viewers, yet still be registered on the search engine. If possible any element of your website should treat both the search engine and the human viewer the same.