This demonstrates the use of min-width and max-width.
Left and right are floated left and right, and are 5ems. Middle is floated left, has a width of 50%, with a max width of 15em, and a min width of 10 em.
Left
mmmmm
Middle
At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd
gubergren, no sea takimata sanctus est.