CSS width 100% OR max-width in pixels

How one could create a C开发者_如何转开发SS rule for width which

• Uses 100% width by default

• If 100% width exceeds certain pixel width (let's say 512 px), then the width is clamped down to this pixel width

I am not sure about width and max-width relations, or how calc() is supported or could express this. This would need to work with the latest WebKit browsers and Firefox 4. IE8 etc. support not needed

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That's in fact the intended use of max-width. If the computed (actual) width of an element exceeds max-width, it will be constrained to the max value instead of going beyond it. Percentage versus pixels isn't relevant.

Declare both in the same rule like this (no need for the calc() function):

#somediv {
    width: 100%;
    max-width: 512px;
}

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If it's block level element it should be 100% by default so no need to declare the width, then max-width: 512px; would curtail it

calc() is not supported very well at all, but in this case I wouldn't think you would need it

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div{ max-width: 512px; }

should suffice.