* Development costs: implementation, customisation, and simple templating (which isn’t simple sometimes).

* Hosting type; hosting cost.

* Number of payment gateways offered, and whether they will integrate with your bank.

* Whether DCC can be arranged, if you sell in different countries. Direct Currency Conversion shows the purchase price in the customer’s local currency, and is a function of payment gateway/ bank integration.

* Does the application support SEF URLs (search engine friendly page addresses) - and to what extent exactly? A ‘yes’ answer here can have many different interpretations (and, realistically, sometimes mean 'no'); the following question is perhaps more specific.

* Are the URLs short and relevant?

* Can you add pure content pages to the front end, since you will need to do this for good search positioning? This refers to 'ordinary' pages with no products on them; shopping cart makers call these 'brochure pages' or 'web pages'.

* Is the admin backend slick, basic, or poor?

* Is there a category page option, with separate templates?

* Do the product pages suit your class of goods or services?

* Are the product pages fully templated, allowing easy customisation? How easy (or difficult) would it be to import your own design?

* Are there 3rd-party developers who can help you customise it?

* Are there region-specific versions that will work well in your area?

* Will you get a large choice of attributes to vary, on the product pages? You might need size, colour, price, and weight options.

* What tax variants can you get?

* What about shipping options? You'll need to be able to specify different shipping methods and costs.

* Can you cross-sell, up-sell, multi-sell, affiliate-sell and auto-apply discounts with it?

* What reputation does your chosen app have for security?

* Is the look and feel of the store more important to you than other factors?

* All shopping carts have built-in SEO negatives; does your proposed solution have less than others; and is therefore better?

* Does the application specifically mention positive SEO benefits over other programs - and are these genuine? Application developers who realise that search optimising is the first priority and not the last are still rare; if you find one, then support him - it will be worth it.

* Does the page code validate 100% out of the box?

* What is the maximum number of products the application supports? Some users will need to know this figure, since there are numerous product types that can approach the 10,000 max figure that is probably the lowest quoted.

* What database (or databases) does the app use? The most common is MySQL, which almost all hosts provide on their servers (including of course Windows hosts). Always choose this if possible.

* Apps that use a 'flat file database' do not use a database as such - it is a text file equivalent, not a discrete application. This imposes size and speed limitations that effectively mean the upper limit for the number of products is about 10,000. An example is Miva4 (though newer versions use a real database and are much more capable).

* Is the application a server-side or client-side program? Some shopping carts are client-side apps that run on a local database, i.e. one on the owner's own PC. The pages generated are then uploaded to the site. There are product number limitations with this method, of the order of 10 or 20,000. One example is Actinic, which runs on a local PC, and can use Microsoft SQL Server (other versions use Access); this app now though has some very good SEO points, and is well suited to stores without a large number of products.

* Does the application as standard come with links on the page (maybe at the foot) to the supplier? You don't want this - certainly on the front page - they will have to be removed. Links can go on the page specifically for that, or from out of content if you are really doing them a favour. Otherwise, they can pay you £500 a year for a link.

* Do the pages have hidden links in the code? You need to check by viewing the page code source. There must be absolutely no <a href="http://www.the-app-supplier.com"> in there. Unless specifically mentioned in the sale contract, they should not be there; and in any case must be removed. Search engines are not happy with anything in the source that cannot be seen by visitors.

…and a hundred other things you need to know first!

Databases

Don't go with a host that only gives one database per site - that is just plain ridiculous. I know of hosts that offer 10 DBs on their accounts, and 5 is not uncommon - it's also a good number to ask for; 3 is the minimum.  Anything you might want to add on or plugin to your web application will probably require a database: web analytics, blog, wiki, etc. There is no cost to the host as they won't have to support subsidiary DB's; and their data size is included in your webspace total, so it's not as if you're getting something for nothing.

In order of robustness (i.e. stability, security, ability to handle large amounts of data), the order of database quality is considered to be:

• a well-known database offered by a large PC operating system supplier;

• MySQL (light years better);

• PostgreSQL;

• Oracle.