chess.html:36:8

means

• file chess.html
• line 36
• character 8

It's not always 100% clear what the line number corresponds to between the original source and the page as modified by scripts after Firefox starts parsing it. It depends on when the error occurred in that process.

Note that you can click the gray arrow that shows at the left side of a message to expand this message and show more detail (trace).

jscher2000 said

chess.html:36:8 means

• file chess.html
• line 36
• character 8

It's not always 100% clear what the line number corresponds to between the original source and the page as modified by scripts after Firefox starts parsing it. It depends on when the error occurred in that process.

That was my first thought. Tut it is actually the 72 character in the line in my editor. so how is that? The line number is correct though, so it doesn't seem like he summed some lines together or something like that.

Maybe there are tabs in the file that are expanded differently in your editor (4/8).