Studies show that Web users tend to ignore graphics, looking at text first. After much searching you find a useful page deep down in a framed site, and want to send the URL to a friend, or link to it from your Website. Search engines often have trouble listing content from sites that use frames. Frames take up valuable real estate on small screens, where the user may prefer to simply have the content on the screen, not an additional scroll bar and an area of content that won't go away. It can be difficult or impossible to print a page in a frameset.
Frames make a page incomprehensible to some screen-readers for the blind.
Here are a few sites that exemplify good information design to one degree or another. Not all these sites are perfect, but each has many of the qualities that make a good Website. A mini-form on the homepage allows you to track a package easily. Subpages maintain visual and navigational continuity by keeping the top tabs and menu bar. Overall the site is highly useful, clean, and conveys a strong identity through color and appropriate graphics.