Some Web developers still include a small 'Website Built by XYZ' or 'Powered by XYZ' at the bottom of each page. The obnoxious action is as irritating as car yards placing stickers on your vehicle's rear window.
While the impact is insignificant, the unwelcome link devalues the weight of links on every page (link weight is assigned based on number of links and position).
Bottom line: no good comes from keeping a link to a web designer on your website. That said, no self-respecting developer will ever include it. If it's there, remove it.
