If you are processing credit card information or storing personal data that should not be exposed, it is important that you have access to a secure server. Security is a growing concern with Internet shoppers and many businesses report an increase in conversions just by displaying a secure symbol in their shopping cart area.
Some web hosts will provide you access to a secure portion of their server. In these cases when visitors navigate to the secure area, the URL will actually change and the visitor will no longer be “on” your site (i.e. www.yourdomain.com). In most cases the user probably won’t even notice, however many websites place their entire online store on these external secure areas. The downside to this is that it removes many potentially valuable pages off your site making any potential search engine ranking benefit inaccessible to you. Each of these pages could otherwise be an entry point to your site via the search engines.
The other option is to have a secure area on your own site. You can do this by purchasing a secure certificate for your domain name. This certificate is then “installed” through your web host giving you unlimited secure areas of your site to work with—all on your own domain. This is the most professional solution and allows you to keep potential search engine friendly pages indexable with the rest of your site.
I would also recommend keeping as much of your website out of the secure area as possible and only transfer visitors to the secure area when they are in the checkout process. If they leave the checkout to continue shopping they should also leave the secure area.