Maybe not unethical, but unwise...?

Some corporate sites do not want you to put a credit link on their site, others have preferred you put it in their 'links' section (if they have one). Ask the client first... it is their site and they are paying for a presence and may not want your ad - no matter how unobtrusive.

I always put credits in hidden tags in my coded pages and like Webnauts I too have a couple sites floating around still giving me credit from 6 or 7 years ago, the sites are a total mess and embarrassing disaster, unfortunately I am still credited for these nightmare sites taken over by employees or family members!

A pleased client will refer you, you don't need the free ad, especially when it turns around and bites you years later.

BIL

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"If you think you're free, there's no escape possible." RAM DASS