There is a vast amount of information on the web, publicly accessible. Qualified observers can assess the technical skill of a web company by looking at a site and the page construction, they can perform complex analysis using validators and sites like http://websiteoptimization.com. They can easily determine the versions of software in use (unless security was done carefully), they can check how many sites have the same IP address (same server).

Clues:

Old versions of everything - site is not currently being maintained. Opportunity for maintenance and hosting upgrades. This can be very low risk if a robust application is in use, and it hasn’t be heavily customized. Same is true for copyright notices.

Broken link to web company - see above.

Poor design and application integration, broken links, missing images - site visitors have high expectations. A bad site can cost a company alot in lost business. A quick link to a demo may help the site owner see the value of your proposal.

Glaring security issues - it is easy to quickly check a site with non-destructive SQL injection testing and invalid data testing, as well as simple certificate checks. Alert the site owner with a screenshot or URL that demonstrates the vulnerability as well as a quick description of possible resolutions.

Scanning sites for information such as older versions of Apache/PHP and applications is reasonably cost effective. A few innovative email templates should allow a professional message to be delivered to prospective clients.

Finally, most sites last about 3 years before they need to be refreshed, improved, redesigned.