While FrontPage's Estimated Time To Download indicator does a decent job of calculating page-load times, it only presents a number. Pages still load just as fast when you preview them over a high-speed connection, so it's can be hard to relate what you see in FrontPage's Preview mode or your browser to what the indicator says.
If you really want to see a site as other people see it, you need a way to temporarily slow down your Internet connection. A great tool for doing that is the Sloppy utility from DallAway. You enter your site's URL and a desired connection speed in Sloppy, and the program launches your browser and loads the requested site at the specified speed. As long as you follow relative hyperlinks within the site, Sloppy continues to slow down your Internet connection. Follow an absolute URL or enter a new URL, and your normal speed resumes.