Although KPIs differ for each strategy, below is an example of typical indicators. This list of possible metrics is not exhaustive, but does shine some light into the ease in which online marketing campaigns can be measured. Every click on every search engine and website is logged! http://forum.girilaya.com/t71-key-performance-indicators-for-a-web-marketing-campaign

SEO
• Keyword Rankings
• Search traffic
• Conversion rates
• No of email enquiries (leads, (CPL))*
• Cost per Acquisition (CPA) of customer
• Customer retention

Traffic
• No of Unique Visitors
• No of Pages viewed
• Length of time spent browsing websites
• No of click through (CPC / PPC)**

Additional KPIs
• Visitors to supporting websites
• Visitors from Viral Marketing / blogging sites etc.
• Increase in Internet Presence (number of links page rank etc)