Does it give me any advantage if I set this header when generating normal HTML pages?
I see that some frameworks out there will set this header property and I was wo
I think its only because of the HTTP Spec says to do this in every case possible.
Applications SHOULD use this field to indicate the transfer-length of the message-body, unless this is prohibited by the rules in section 4.4.
You can also look at Pauls Answer on the Question of Deaomon.
I think this will answer yours too.
Also you should use Content-Length if you want someone download a file with another header: e.g.