It depends. How long is a piece of string? How high is “up”?

Too many variables for a cogent answer. What kind of software is being used? Is it a plug and play program like Dreamweaver or are they actually coding? How capable is the teacher? How fast a learner is the student?

What do you mean by “code?” Is it just the HTML/CSS that make up the visual layout and textual content of a website? or are you thinking of a dynamic site (like Fluther) that involves actual programming where users can submit information, create accounts, etc. because that’s a whole other separate thing.

When you say design a website, are you talking about learning the principles of graphic design and layout as well, or are you assuming the person already has the aesthetic/usability knowledge for how to layout a page for ease-of-use, with good contrast, proportion, scale, fonts, colors, etc.

On the short end, you can learn to write the CSS/HTML for a very simplistic static website in an afternoon. It would probably take 6 months to a year to be able to learn the programming skills necessary to build a site like Fluther, and that’s assuming you’re working at it full time, and you already have the visual design background to understand good techniques for organizing and laying out content on a page. Also the quality of your code will be very amateurish at that stage.

It could take 3–5 years of full-time programming experience to write a site like Fluther from scratch and have the code be well-designed, secure, efficient, easy to make changes to, etc. Programming is a lot like learning to write well. You can write simple, grammatically correct English sentences that accomplish your minimum goals of communicating x, but it takes years to master the art of writing well to communicate x with an artful fluency.

I hope that helps clarify things a bit.

Thanks. Great answers all.