Summary: Most site maps fail to convey multiple levels of the site's information architecture. In usability tests, users often overlook site maps or can't find them. Complexity is also a problem: a map should be a map, not a navigational challenge of its own.
One of the oldest hypertext usability principles is to visualize the structure of the information space to help users understand where they can go. On today's Web, site maps are a common approach to facilitating navigation. Unfortunately, they are often not very successful at it.
Users Don't Know About Site Maps
We conducted a usability study of site maps on 10 websites, and our main conclusion is that users are reluctant to use site maps and sometimes have problems even finding them. Considering that site maps could be particularly useful to people who are lost, it is not good news that they are often hard to find. (See also update with newer research .)
In our study, we asked users to try to understand a website's structure and organization. Even though all of the study sites had site maps, only 27% of our users turned to the site map when asked to learn about a site's structure.
Later in the study, we specifically asked users to go to the site map. Some users simply couldn't find it ; we had to point out the link to the site map 27% of the time.
Even more striking was the fact that users were unaware of the site maps on sites they visited on their own. We asked users to show us sites they had used recently. On those sites that included site maps, users were aware of them only 15% of the time.
The main reason users don't expect to find site maps is that less than half of all websites currently have them. For example:
- 48% of the sites surveyed for our recent book on Homepage Usability had site maps, and
- 45% of the sites our study participants selected when asked to go to a recently visited site had site maps.
Users won't search out the site map on their own. Forcing them to navigate to a navigation aid when they are lost adds insult to injury. Thus, we strongly recommend having a clear link to the site map on every page. Call the link Site Map . This label worked well in our study, and is the one used by 63% of sites with site maps.
Using Site Maps
The site maps in our study were fairly successful at getting users to destinations that were included on the maps. On average, users visited 0.3 erroneous destinations for each task that asked them to go to a page linked directly from the site map.
Even though 0.3 errors per task is fairly good, this error rate indicates that many site maps are overly confusing and not sufficiently supportive.
Erroneous clicks increased to 1.1 per task when we asked users to perform tasks that required going to pages that were two clicks from the site map, rather than directly linked. The fact that the error rate increased by almost four when the destination was not directly mentioned on the map is a strong indication that current site maps are not good enough at communicating the site's information architecture .
Users go to site maps if they are lost, frustrated, or looking for specific details on a crowded site. CDNOW had one of the most successful site maps in our study, partly because the site map was much calmer than the busy homepage.
CDNOW's homepage and site map.
Many users prefer to simply use the homepage to get an overview of what a site offers. Users also commonly rely on search or navigation bars that are included on most interior pages. The site map must add something extra to these standard navigation methods.
A site map's main benefit is to give users an overview of the site's areas in a single glance by dedicating an entire page to a visualization of the information architecture. If designed well, this overview can include several levels of hierarchy , and yet not be so big that users lose their ability to grasp the map as a whole. Some of the site maps we studied stretched over six screens on a standard 800x600 monitor. This is much too much. We recommend keeping the site map short ; it should be no more than two-and-a-half times the window size most common among your users.
The greatest failures in our study came from site maps that attempted to lure the user into a dynamically twisting and expanding view, rather than presenting a simple, static representation of the information architecture. The site map's goal is to give users a single overview of the information space. If users have to work to reveal different parts of the map, that benefit is lost.
Dynamic site maps are basically an alternative way of navigating through the information space using a set of non-standard interaction techniques. For example, one site used a hyperbolic tree, where users had to click and drag clusters of links around the screen to expand areas of interest. Nobody could do this well.
A site map should not be a navigational challenge of its own. It should be a map.
As we have found again and again, users hated non-standard user interfaces that forced them to learn a special way of doing things for the sake of a single website. Site maps should be simple, compact layouts of links, and they should show everything in a single view.
Future of Site Maps
Anyone who has been to a shopping mall knows the value of the "you are here" dot on the map. Site maps must become more aware of users' website navigation, indicating not only their current location, but also site sections that they've already visited. Site maps that use textual links and standard link colors already offer a simple version of the latter feature, changing the color of links to visited pages. Unfortunately, users cannot see whether they have visited pages deeper within a section of the site, and better awareness of the user's navigation probably requires some amount of integration with the Web browser.
I have often predicted that Internet Explorer version 8 will be the first decent Web browser. One feature request for version 8 is better navigation support by offering a visualization feature that would pull the site map out of the website and make it a standardized browser element. Unfortunately, waiting for Microsoft is not for the impatient. If you wait long enough, you might become King of Sweden, but we can't wait for Microsoft as our only hope for improved website navigation. Even without browser integration, site maps could help users much more than they do today. Please focus on usability in site map design. Keep them simple, and emphasize a compact overview of the information space.