syntax explanation???

What is this good for to write two template names after each other like this:

.active-scroll-left{width: 150; height: 40px; }
.active-scroll-left .active-list-item {width: 150; height: 40px;}

???????????????????

Thats obviously a mistake - '.active-scroll-left' refers to the fixed column on the left side, while '.active-scroll-left .active-list-item' is a row header box. So the sizes should be different at least...