I am not a big fan of putting external links in the foote. It's more a place for “about” section and copyright information. If I want to compliment or say "thank you" for something connected to webdesing I would create a separate page for that and list. From the designer company point of view it would be even more logical to do that. Sidewide links suppose to have less juice that they used to.

I don't think there is much wrong with citing who did the design work as long as both parties are happy. However, it can also be viewed as parasitic and in some cases the main source of link building for a design/seo company.

I have used this before and gained business from having my link there, because people liked the work then saw the link. Although I have released sites that have no citation as well.

I'd agree with the first commentator, "it's a matter of personal preference."

I do it, not for the SEO value but for two reasons.

1. Repute - I've landed some clients that found me from the footer link of competitors/suppliers. Sure I may have gotten them anyway, but having a link certainly does no harm in this respect.

2. Other web designers - I'd say most of the people that click these links are other web designers. I know I often look out for who made what websites in my local area.

I've actually been asked by clients to put this link on their site! I think some people view it like they view the badge on their mercedes. A bit of a makers mark.

It's at the bottom of the site and is almost meaningless to G, except the number of links you get for it being in the footer of a site.

But, as always it is up to the website owner..

I think it is perfectly acceptable. It has helped me choose software providers in the past. It can help people choose Web designers as well.

If you've spent bucks SEOing a site you want people to stay on it once they're there. You don't want to present them with invitations on every page to go somewhere else, even if it's off-topic. If your web designer wants a link, then give them a link from the resources page, that's what it's there for.

Its VERY common, after all, doesn't this site do the same? It links up RustyBrick Web Development in the footer.

Dont expect much SEO help from it for some websites. Results of the benefits they carry from one site to another will GREATLY vary. I see this every day for sites I manage.

One simple question. How does Google diagnose what and where a footer is? Because it is the last piece(s) of code in the HTML? Seriously that would only require moving the code higher up right? Now no more footer links????? Confused.

If you're placing a link to your company in a client's footer site-wide, it will have little or no value as far as search engines are concerned. The key is to put it on one page ONLY (preferably the home page). That looks much more like an intentional "vote" and much less like an advertisement...and therefore brings more value.

Why do you suppose you don't see people create a page dedicated to the designer/developer, per one of the first suggestions & link to it from all other pages?

I don't think there's anything wrong to give credit to the company that sponsors the theme. Basically it is offered free by the designer because someone else is willing to spend the money for it to get developed. Likewise, if there's no monetary support, the theme would not be created in the first place. However, I would most likely reject a theme that has too many footer links (sometimes up to 4) which I think will end up hurting your site instead as it becomes too spammy.