"You have not visited the demo pages yet," teases a Web site. A background color changes to a shade chosen by the visitor. And a new message or banner appears as a user navigates through the site, chosen to appeal to that person's particular interests.

How can a Web site do that?

One way to accomplish such personalized touches is to store various version of a site on a server and use Common Gateway Interface (CGI) scripts. Web Threads says it con offer another way. WebThreads, a spin-off of Vienna, Va.-based Image Communications, helps to tailor a Web site's presentation based on a visitor's actions and choices through the site. the software can enable site developers to have visitors showered with different messages that may encourage a particular path through the site or or might entice the visitor to click on an advertisement, said Jeffery Spillers, vice president of business development for WebThreads.

WebThreads tracks and reports on user activity at a site while enabling interactive customization in real time, Spillers said. The reporting function does not rely on the log file but tracks visits to pages on the site on a per-user basis. A number is assigned to a visitor, and the visitor's path through the site is tracked.

The tracking reports show how many users visited during a specific time period, which pages were seen by each user and when, and the most popular path through the site, among other data.

The product, priced at $895 and available immediately, will help Web masters gauge the effectiveness of elements of their site and make adjustments accordingly, Sillers said. WebThreads also is aimed at financial institutions wishing to create online banking applications. A professional developer's edition is scheduled for next quarter.

The product works with any browser and server software, said Yermo Lamers, chief technology officer for WebThreads. The product takes away much of the management burden of a Web site, he said.

WebThreads won't add to the number of programmer needed to maintain a site, said Chris Stevens, analyst for the Aberdeen Group in Boston. Like many other traffic analysis products, WebThreads is limited by the inability to identify a user from session to session, Stevens said.

WebThreads' counting function competes in the tracking analysis fields. Other off-the-shelf site traffic monitors include Interse's MarketFocus, net.Genesis' net.analysis, and Bien Logic's SurfReport, among others.

Also last month, Softbank-funded Andromedia introduced Aria, a traffic analysis tool that will ship in the third quarter of 1996. The product is expected to be priced from $1,800 to $35,000, depending on hit volume and system configurations.

The San Francisco company, which has 14 employees, intends to bundle Aria with Web application products. Andromedia is also marketing the product through direct sales to Web sites and Web hosting service providers.

Andromedia recently partnered with New York City-based K2 Design, Inc., a company that develops corporate Web sites. K2 Design will be a channel partner and will include Aria in its suite of offerings.

Leslie Howard, vice president of product development for K2 Design, said she uses Aria because it is scalable and can show a user's navigational path through the site.

"Their solution really can handle the high-end sites," Howard said. "It's immediate. That's meaningful as more and more sites grow to the over-1-million-hits-a-day category."

The Aria system includes the Aria.monitor and Aria.recorder components. the monitor resides on the server as a linkable library, monitoring the connection between the user and server. Capturing information passed between the client and the server--such as cookie profiles, form field data and standard log file information--the monitor sends it to the Aria.recorder module.

The Aria.recorder can run on either the same machine as the Web server or on a dedicated server.

Aria supports the Netscape Navigator, Microsoft Explorer, Mosaic and Spyglass browsers. It is compatible with Netscape Commerce Server and Netscape Communications Server.