Blaming myself actually costed me a lot of time (I do it naturally, never had to learn or think about it). For example asking myself what in the world I could possibly be doing wrong (php echo's which just weren't working and such), and then learning about 15 minutes later that the FTP was failing to update the file because the classmate still doesn't know how to set FTP permissions (he chmodded one includes folder to 777 for me, leaving still no access to any other folders -.-). From the other side, I can imagine that it also could have costed me a lot of frustration and time if I blamed the software I was relying on right away. Now I've experienced a couple times that it was not my fault (while often it was my fault :p), I think I've found a pretty good balance. The underlying system is usually not thát hard to check, so after about 10 minutes of troubleshooting (10/15m is usually enough time to go through most of the possibilities) I start checking the system.