why do I need a SSL certificate (https connection) on my ecommerce site?

Your ecommerce website needs to have a valid SSL certificate installed and running.
Here’s some background and reasons why:

What’s does a SSL certificate do?
A Secure Socket Layer (SSL) certificate does a couple of things:
1. encrypts information entered into a form
2. checks the integrity of the connection between the browser and the server (are you connected to the correct server?)
How can I tell it’s working?
The address bar will show a padlock and the word https:// in front of your website name on pages that require SSL encryption.

Note – there is no advantage in making all pages on your site https:// – it works with pages that have forms. Technically, https:// will slow down page loading speeds of your site and also may interfer with indexing by search engines. Most oscommerce-based carts have certain pages where https:// connections will be made, in particular logins, creating accounts and checkout.
But SSL certificates and https:// connections are just for payment pages though right?
Not true – a SSL certificate scrambles data and secures connections when any form is submitted (a form is basically what it sounds like – anytime you type information on a website, you’re probably filling out a form of some sort.)
So this means your admin and customer logins, contact us and create account pages as well all benefit from your server having a SSL certificate.
And if I don’t use one?
All of the data submitted will go as clear text, ie unencrypted. It is possible for unscrupulous people to set up ‘sniffer’ and ‘listening’ scripts and grab those clear text details being sent, which could gain them admin login details, customer address information as well as payment details.
Also, the server may not in fact be the server you or your customers intended on reaching, as the integrity of the link will not have been verified to any extent.
Implications
Customers are now very aware of the https:// symbol in an address and if they don’t see it when they go to complete an order or set up an account, most will leave.
Identity fraud is a major industry around the world, so it is strongly recommended that if you want to get the business, you operate with a good SSL certificate in place and advertise the fact. Really, it’s a bare minimum to be in business online.
Furthermore, some payment gateways and processors require you as a merchant to have a valid SSL certificate installed before you can connect to them and use their services.
How do I get a SSL certificate?
There are a couple of ways – 1) contact your hosting company to set one up, or  2) Do It Yourself (DIY)
Installing a SSL certificate is not difficult as long as you have access to the interface needed. If you use cPanel, you can use the TLS/SSL Manager in the Security box on the right. Create a CRT and private key, go buy the certificate and supply these parts, generate certificate, copy emailed certificate in certificate box, install – done.
If you don’t have access to the necessary interface, contact your hosting company and ask them to install the certificate.
Most SSL resellers like RapidSSL, Geotrust, Verisign, Digicert etc have instruction sheets to assist you as well as online support.
SSL certificate prices range from under USD100 a year through to bank-level EV SSLs with multiple verifications (ie way over the top) costing much more. Get one that fits with your business volume and turnover – but most importantly, get one!