Files name conflict

Yesterday at office, trying to solve Jomsocial issue's. Initially i didn't figure out it so i googled for the answer but couldn't find what i was looking for, checked on Jomsocial forum still didn't get. After spending half an hour got a link where i got what i wanted. There were two files opened in my text editor one from local & other one from live server. I made the changes in local file & was checking the output on live site. I spend half an hour & thought that this solution won't work for me. So again i googled but i got nothing which really take me out from this situation. While googling i realised that internet speed became slow, then how could that changes were fastly done in live file. When i look at editor's tab there were two file's opened. I made change in correct file & it worked. At the end wasted one an half hour for the task which could take half an hour. It happens sometimes when you lost concentration. Well i hope it wont happen again..