While applying KVL it is not necessary to have the loop traversing direction and the current direction the same. e.g. the loop could be traversed CW and the current direction could be CCW. But in some situations having the directions for the both current and loop could make things easier such as in mesh analysis. Further, the direction of current defines the polarities of the resistors because the current flows from higher potential toward the lower. If a resistor is traversed in the same direction as the current, then the IR term would have -ve sign, otherwise it would be +ve.
In the linked diagram if we star traversing the loop from point "a", then the equation would be:
+E - IR1 -IR2 = 0
I will ask some questions later. Please correct me if you find something wrong. Thank you.
I thought this might be of some help to someone like me who reaches this thread. Please have a look on the link to notice another important point about the KVL: https://img97.imageshack.us/img97/9497/img0001xj.jpg
As mesh analysis is also an application of KVL, therefore what is said about KVL above is also applicable while using mesh analysis. For example, in the linked example, current directions and loop traversing directions were chosen arbitrarily. But answer was still correct. It should be noted that equations might appear simpler if there you use similar approach for all loops. e.g. If you traverse the loop in the same direction as the current in all the loops and all the loops have current running either CW or CCW, then it might make things simpler to solve.