[ksa]

Как вариант...

var css='background-image: url("http://mysite.ru:8080/img/environment/circle_portret2.jpg"); position: absolute; top: 73px; left: 93px; background-position: 0px 0px; background-repeat: initial initial; ';
var re1=/(^|;)([^:]*)/g;
var re2=/(:)([^;]*)/g;
do {
	var prp=re1.exec(css);
	var val=re2.exec(css);
	alert(prp[2]+'='+val[2]);
} while (prp!=null);