By default, both the cache_store_log and access_log are disabled. You can enable either by commenting out the following two lines in the C:\ClientSiteProxy\etc\squid.conf. Then restart the proxy service.
Table: Interpreting the CSP logs
Example c:\ClientSiteProxy\var\access.log
192.168.0.11 - company\administrator [11/Oct/2006:12:34:18 +1300] "GET http://www.mozilla.org/images/header_tab.gif HTTP/1.0" 200 4816 TCP_MISS:NONE 192.168.0.11 - company\administrator [11/Oct/2006:12:34:18 +1300] "GET http://www.mozilla.org/images/header_br.gif HTTP/1.0" 200 1064 TCP_MISS:NONE 192.168.0.11 - company\administrator [11/Oct/2006:12:34:18 +1300] "GET http://www.mozilla.org/images/header_tr.gif HTTP/1.0" 200 984 TCP_MISS:NONE 192.168.0.11 - company\administrator [11/Oct/2006:12:34:18 +1300] "GET http://www.mozilla.org/images/key-point_back.gif HTTP/1.0" 200 610 TCP_MISS:NONE 192.168.0.11 - company\administrator [11/Oct/2006:12:34:18 +1300] "GET http://www.mozilla.org/images/header_tl.gif HTTP/1.0" 200 1354 TCP_MISS:NONE 192.168.0.11 - company\administrator [11/Oct/2006:12:34:18 +1300] "GET http://www.mozilla.org/images/header_logo.gif HTTP/1.0" 200 5682 TCP_MISS:NONE