There are CSS hacks for IE that does work, but there's quite a few of them:
hasLayout
hasLayout: true;
--- Apparently forces IE7(?) rendering to follow CSS layout rules for the element instead of global rules
*display
*display: inline;
zoom: 1;
-- The star hack, which apparently "tricks" rendering engine to line up the divs as inline elements
float
float:left;
-- Good old float, even IE6 should support it, but I don't know why you should be worried about IE6 although Chinese browser statistics seem to indicate that IE6 is still pretty popular in China, yet that could be already history as I read it some time last year. Personally, I think North Korea shouldn't be a worry, but that's just me.
However, there seems another way to avoid all those hacks in favour of a google online code project called HTML Shim, or Shiv. The purpose of including it is to make all IE versions before v9 to support HTML5. I noticed that it helps and I don't have to use all of the above to get inline-block to work. This is only valid if you don't mind adding some JavaScript. On the other hand, who does without JS these days?
Of course, there's also the quirks mode (compatibility) or standard modes, so take care to add a valid doctype to start with. For HTML5, it's simpler:
<?DOCTYPE html>
(?) Not sure about which version, but I think I read 7 in quirks mode.