Our Seaside application is currently running in cooperation with Apache HTTP Server with no problems at all. However, at the moment we are requested to support Internet Information Services on the server side instead. Unfortunately we do not have any experience in running Seaside application in combination with IIS yet. Can you provide some assistance on what and how should we configure to make it work?

You need an ISAPI plugin for mimicking the proxy and reversed proxy behavior of Apache. That way you can redirect to Seaside running on some local port, and you can split static (CSS served by IIS) from dynamic (Seaside) content.

One of our customers is successfully running the desired setup with a product from a company called Helicon Tech. The product, ISAPI_Rewrite, is an IIS-plugin which implements the functionality of apache mod_rewrite and the like (it's even syntax-compatible). Note that this product is not free. However, there are free alternatives, just Google a bit.

The customer is running a high-volume website behind it. Static content is served by rewriting to IIS (something like RewriteRule ^/(seaside/files.*)$ http://localhost:8788/$1 [P,L] and the dynamic content is served by a Seaside instance on another port.

You can find more info on http://www.helicontech.com/isapi_rewrite/.

If you are running IIS 7.5, Microsoft provides official support.

In the site settings, you'll get an "URL Rewrite" icon.

In this dialog you can enter the hostname + port to forward to. After adding the rule, opening the edit dialog offers more customizations.