Traditional web design and development are rooted in the concept of a Multi-Page Layout, or MPL. Contemporary web design and content management systems have transitioned towards a Single Page Layout, or SPL.
MPL web sites store their content in individual web pages. Adding more content requires adding additional pages. SPL web sites use a single web page template that derive their content from a database. Salesforce.com makes a great database for managing both content and Leads/site members.

Many organizations gradually wade into developing unique landing pages for Google AdWords or publishing products and services. At first, the MPL approach provides the path to least resistance since initial development and deployment costs are fairly low. The cost of change remains fairly linear at first as each new page is cloned from an existing page and modified to suit the campaigns needs. But over time the cost of change begins to increase. It takes longer to provision new pages and development becomes much slower.
A form of "technical debt" is accrued whereby a developer must eventually externalize common UI elements to server side include (SSI) files, such as headers, logos, navigation, and footers. Even with SSI best practices in place, a developer/programmer still remains in the critical path for each new campaign and the skills required for ongoing maintenance remain high.
SPL templates may take 3-5 times longer to initially implement, but successive pages may be easily provisioned by business users, such as Marketing and Support admins. The time to provision a new page remains linear over time as each new page is defined in a database and immediately available for use in PPC campaigns.

SPL page templates are actually very simple to develop. They may look slightly cryptic when opened in a common web page designer because they contain "merge tags" to be replaced by the database when the page is displayed. The URL typically contains some kind of unique ID to give the page context as to which content to display.

i-Dialogue 8 now supports a new scripting language called Dialogue Script that removes the need for a physical page template. The SPL template can be created directly in a web browser and the merge tags can define any Salesforce object or field.
The Professional Services group at Cubic Compass Software has extensive experience with SPL design and hosting. Contact me for more information. I'd be happy to help.