Max-width always work, but when I enter mind-width: 800px; it never works.

I can still narrow the browser window until the design breaks.

I use floats, no absolute positioning, and this is the second design where min-width doesn't work.

What could be the reason?

In which browsers?
Internet Explorer 6 does not support this property.

In Safari 3. Should work there.

Nobody?

I put it into the body CSS, then at least max-width works.

If I put it into the wrapper CSS that wraps all divs, both max-width and min-width don't work.

Sounds like a bug in the WebKit engine, have you tried a search for Safari3/webkit bugs ?

I got it to work in Safari.

Now it doesn't work in Firefox.

It's a fluid layout with three columns in percentages. Large gutters.

In Safari, the gutters narrow equally.

In Firefox, the gutters only narrow on the left, stay the same on the right, and the column in the middle starts overlapping the left column, while to the right there is still the original gutter (which is also in percentages. But it doesn't shrink in Firefox).