a web site is provisioned with a proxy that receives a page request intended for the server and records a first time . the page request is then forwarded to the server for response . the response stream generated by the server is intercepted at the proxy at a second time . as the stream is forwarded to the requesting client , the proxy inserts a page script that , upon execution at the client , calculates a page render time . this time is determined by calculating the difference between a third time and a fourth time . upon completion of the page rendering , the script opens a connection back to the server and returns a packet that includes the page render time . this packet is received at a fifth time . a transaction record is then built by the proxy using the timestamp data .