I’ve just had an enquiry from a perspective client in which he asks for “guarantees in terms of quality, usability and search engine visibility”.
I’m confident that I can achieve the highest standards in all those but how can I guarantee it? I’m not sure what to put in writing for the quote.
Any suggestions?
You can’t guarantee those things because those things are subjective.
If he can define quality, usability and search engine visibility then you could, theoretically, make a guarantee but even then I wouldn’t try to.
You can’t guarantee a first page placement in Google for one.
Agreed, he’s asking for the impossible. None of those things are measurable as they are all subjective and dependant on factors you can ultimately have no control of. Not to mention that the factors themselves physically change on a regular basis. What might be highly usable, flexible, beautiful and visible one week, may well not be the next due to search engine updates, changes in common conventions, usage or customer requirements, etc. The more theoretical arts of web design (which he wants the guarantee for) require constant development and upgrading on a long term basis, it’s not something that has a fixed viability. 
I can only agree with what’s been said, but here’s my thoughts:
Quality - what do they mean by “quality”?
To me that would be sematic coding/HTML, accessibility to maybe level AA, and something that meets the aims of the sites visitors, using a defined measurement for the success criteria.
To your client it might mean something completely different like using the right colour shade!
Usability - usable for who?
You can make the simplest site in the world and someone, somewhere will find it hard to use!
Search engine visibility
So long as you don’t make any huge blunders you can normally be confident that SE’s will start indexing a site, never guaranteed though. The problem here is that sites can be indexed but don’t show up until page 50, they are still visible to someone who visits page 50 but your client won’t see it like that.
Only if an objective definition of exactly what is meant by those descriptions is agreed to can you even consider whether you will be prepared to guarantee it.
You could define quality in terms of compliance with standards. For usability you’d need to clearly define the criteria under what circumstances the site needs to be usable. For search engine visibility you’r definitely need to specify search terms and a time limit.
It would cross my mind that they are looking for a way not to pay me after all the work is done, and I would seriously have to have a talk with them about what they are looking for and what I would be providing, and make it clear to them that there would be no absolute guarantees.
As much as I hate to agree with this I thought the same thing. By asking for such subjective guarantees they have a perfect ‘out’ if the want it and there would be nothing the developer could do about it.
I would tell them that if they could lay out in exact terms the definition of those things and I could then agree to those definitions then we could go forward.
I think all three are measurable and therefore can be guaranteed. You just have to be reasonable about what a guarantee is:
“Guarantee - a written assurance that some product or service will be provided or will meet certain specifications”
Search engine visibility
Let’s take the easier first, search engine visibility is simple to prove. Do a ‘site:’ search a few days or weeks after the site goes live and you will see all the pages that Google has indexed therebye proving visibility. Simple. If you can’t see anything you’ve failed to meet your guarantee but let the client try to prove that… you can always say, wait, they’ll show up!
Usability
Usability is a little harder to prove but still not impossible by any means. Usability is simply how easy to use a website is and there are acceptedguidelines for it. So assuming that the site has a purpose (and all should) then you just need to establish some goals for the site, plan how they will be met (Information Architecture), and then test to see how many users complete those goals. If you hit a previously agreed target you can ‘prove’ Usability. If you’re not willing to agree to the targets and guarantee them, then don’t!
Quality
I’d also argue that in a court of law I could argue the ‘quality’ of my product since the definition of quality is: “The collection of features and characteristics of a product that contribute to its ability to meet given requirements.” (Source). Also easy to quantify.
Sure there is, that’s what contracts and deposits are for 
I think it all hinges on what tke said a few days ago:
If you can agree on criteria that define - for the client - what quality, usability and search engine visibility are, you can potentially measure those. You aren’t actually measuring the subjective quality, though, you’re just measuring a representation of it. The map is not the territory and all that.
The difficulty comes in creating a “map” or measurable representation of those subjective qualities that you can both agree on. If you define “search engine visibility” to be “existence of pages in the index”, that’s very easy to measure. Most clients want a little more than that though.
Carry on. 