Believe it or not, something like this will do:
.element { left:0; right:0; position: absolute; width: 100%; //would be nice, also }
You can also center the content using text-align. Now as for width, some say that it is required, but in many cases I didn’t see any difference (I guess this is dependent on the browser). And you’re encouraged to add max-width combined with width:100% values.
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