Is their any way to specify a dimension (margin, top, left, etc.) in CSS usign both a pixel value and a percentage, something like "70% + 50px", This woudl be very useful in my three-column layout.

Eh .. are you sure you need it? I recommend you re-think the sizes a bit. I don't think you can do that. Also, avoid using absolute values. Try to keep your website "100% resizeable".

Yes, there are times when this would be very useful. I've been doing a lot of CSS, and after cross-browser issues, this is one of the biggest problems I've had.

It would be useful to do this where you're trying to get graphics (which aren't resizable) into your page so that they don't mess up the layout when you resize the page.

It would also be nice to be able to specify a percentage and then subtract a number of pixels; without this, you can never use 100% of your area, because you have to compensate for a margin or border (which are in pixels, and therefore mess up a percentage-based layout)


To answer the original question: no, as you've found, you can't do this directly. But if you're trying to make a column-based layout as you describe, you depending on the result you're trying to achieve, you might be able to get what you want using margins and padding (or even borders, at a push) --
eg width:70%; padding-left:25px; padding-right:25px;

Margins and padding do similar things, but work subtly differently, so try them both, and combinations of them, and see what works.

Hope that helps

It seems to me this is just trying to take a short cut. Or find a quick method of implementing an idea when you could try and search for a diff. idea.

I *too* have written quite a lot of CSS. I've created enough sites using vim [and not just the "text-only" kind] that I can write XHTML 1.0 Strict / CSS 2.0 directly [validation is just a formality].

All I'm saying is .. I've never had this problem .. but sure .. why not ..

Good luck with finding a fix.