What do max-height and min-height do?

[msphelix]

As far as I can tell anything I can do with max-height, max-width, min-height, and min-width I can do with height and width - what are they suppose to do that only they can do?

[ShadowMage]

They specify the corresponding min/max values. For example, min-width: 200px will not allow the element to go smaller than 200px wide. The effects of these properties aren't easily noticeable (especially the min- properties) until you resize the browser window. The max- values prevent elements from getting too big. So if you set a max-height and you put a lot of content in an element, the element will only be as tall as its max-height will allow. Content that doesn't fit will be displayed (or hidden) depending on the overflow property. Usually, that means the element will become scrollable.

[boen_robot]

The effects of min/max-width/height become most apparent when width/height use relative units, while min/max-width/height use absolute ones. With those combined, you'll be saying, for example "Have this element 100% (width) of the window width, but if this width is less then 100px (min-width), stretch it to be exactly 100px, and if it's larger than 800px (max-width), shrink it to 800px".