You are most welcome; I hope you find my feedback useful :-)
Ok, let's get started:
Firstly, I understand some parts of this are still under development, so apologies if I pick up on something you already plan to change, but as I do not know what these things are, you may get a few responses you were already aware of. Hopefully there will be a few things that are new too.
a) Upon landing on the main homepage my first impression is you are linked to the food industry (love the logo) – mainly from the imagery and this is confirmed when I read the right hand column. I must admit however I didn't read the right hand column straight away as it is under the title "Why choose Zest?" – but on my first look at the page I am more interested in "What is Zest?" (I wouldn't choose anything unless I knew what it was first) – which I did figure out but was a by-product of eventually reading that right hand column which was not immediately apparent to me. My point is, as Steve Krug states "Don't Make Me Think!" – a great read if you want to learn more about the art of usability when designing websites – one aspect of web design that is very important and ultimately translates to a better return on investment if you get it right. In the world of ecommerce this also leads on to A/B split testing to find the optimal layout for your site to give the best ROI. Sometimes even the smallest details like "add to basket" vs "add to cart" can make a difference in conversion rate.
b) Following on from this, in case you were wondering "why didn't he click the about us page" – I did - but later – my point is the majority of people online are very lazy – even Google constantly optimise their site so people have to click less – you can now search just by typing and you don't even have to press enter! This is the extent of laziness we must cater for! If they can't find what they want to know with the minimal effort, they will simply click elsewhere because other sites will provide them with that luxury of not having to think to get what they want. Sure once you have gained their interest they will click the about page, but you must capture that interest and trust first, at first look they are just going to have a quick skim. The opening paragraph on your about us page is superb, I would rather see that quoted on the front page in nice large font. That explains a lot more to me than "delivering fine fare" which depending on dialect may not even mean something to everyone.
2) Along the lines of usability, I think your top level navigation could be more prominent – I almost missed it with all the other text around it which is much larger. It is almost like it tries to squeeze in to fit the design, rather than have the design fit the content.
3) As I said to Ruth, content is king, so don't be afraid to put whitespace to good use – you don't need to fill every pixel on the screen, sometimes less is more – currently I feel like the front page is very "busy" as everything is squashed together – there is a lot of information to digest. This leads to my eyes to not knowing quite where to look next. This is easily fixable with a bit more space between elements and some clever positioning of elements to ensure it still fits on a 1024 pixel wide screen, or to move some things to other pages unless they are absolutely required.
A good practice to do is to go through every piece of content on the front page and really ask yourself, if I took that away, could the visitor still achieve what they desired easily? Or what value does that add? If the answer is yes, or none, then put it elsewhere. If it is an unsure, or a little, then put it in a not so prominent place eg the footer or sidebar. People tend to scan a webpage in the shape of a giant "F" – put your prime content you want to be noticed in these regions.
A recent study shows you have less than 50 milliseconds (1/20th of a second) to capture a new visitor's interest. In this time they will decide if they want to stay on the site or not.
4) When I click "start shopping" it takes me to fruit and veg – why is this – I didn't ask for fruit n veg? Given that you have all your categories on the front page, I even go as far to question why this is in the top level navigation to begin with as I would just click one of the categories to get started? Feels redundant to me. If you did keep it then I would move the thumbnails of the categories to the "start shopping" page, and replace all that lovely whitespace gained with some really tempting imagery of your produce (you know really sexy shots like M&S do – its not just food, its M&S food – really build that quality in to the brand) and maybe highlight your products of the day/season or any special offers you have.
5) Once again in the footer we have a repeat of all categories – which is duplication. I would drop the food categories from the footer and keep the footer simpler. Too much text! If I need to get to categories when shopping they are always listed on the left anyway, so I don't need them in the footer as well. This space can be used for something more useful or to keep the footer from looking over cluttered.
6) On pretty much all pages asides from the front page, the right hand green column is not fully utilised. Eg if I go to "tell a friend" there is a huge green space. Maybe you could have some snippet of information like a randomized customer quote from your database, a top tip, or something along those lines.
7) This point is fairly minor, but being a perfectionist I shall put it here for completeness. Your website is specified as being XHTML Strict – this is great – but it doesn't quite pass validation. The errors and warnings are very simple to fix, and if you didn't, probably won't be the end of the world, but you may as well just to be perfect. Ask your web developer if you are unsure, but it should take no longer than 5 mins to make these 3 changes to get your homepage to validate correctly.
8) Finally, but probably the most important too – on your sign up page (and your login form) – the form used to register with all their personal information is sent over a non secure connection (as is the login data eg email and password). Personal data such as this should be sent encrypted over a secure HTTPS connection. The data protection act states companies must take reasonable measures to keep personal data safe, and this would count as a perfectly reasonable measure to implement in today's digital age where this is expected.
Why should one do this? Well if anyone was to use your site currently on say public WiFi to register, a malicious person could capture this data when they send it unencrypted to your server – and thus get a full copy of their personal details.
With programs like FireSheep becoming more popular – this is even easier to do too. To fix this you need to purchase a basic SSL certificate that supports strong encryption. You then install this certificate on your web server, and enable SSL. You then ensure when you send data from the form the client fills in to your server you do it over HTTPS instead of HTTP and then your data is safe from prying eyes.
I hope the above was useful, overall your site is certainly a lot better than many I have seen in my time as a web developer, but it is that last 10% of changes that can really make it shine to turn it around from a good website, top in class website. Do let me know how your site develops!