This is the most important things that you have to know first before trying to change your layout.
Usually people just copy and paste the template script in to their blog editor.
But this is the wrong step.
When doing this, your scripts sometimes could change the character inside the script. This is the different using paste and upload the script.
The different is the ' character and ` character (look at the red color character)
When using copy paste, the script could change and makes your template error.
Do not blame yourself or others because of this ;p
The most thing that you have to remember is
That's all important thing when you decided to change your blog layout.