excellent your code now work and if I try to access to an url who contain the attribute I get this message:
The requested resource
is no longer available on this server and there is no forwarding address. Please remove all references to this resource.
Additionally, a 403 Forbidden error was encountered while trying to use an ErrorDocument to handle the request.
But now I get also a error 403 and I don't know if this is a good thing.
In fact like you have probably understand, I try to remove all url of my site who contain the attribute fontstyle=f-larger OR fontstyle=f-smaller because those url was a case of duplicate content and Google don't like this.
MY Joomla template had 2 button who allow to increase or decrease the font size in all page of my site and give this choice to visitors. That mean my site is more less indexed 3 time by google:
1) With normal font size
2) With big font size
3) With small font size
After discovering this problem I removed those "font size button" from my template, but is now too late because all my pages are present in google index.
For informations here a list of common error about HTTP status codes with some google comment:
If you read about error 410, google suggest to use also an error 301 an redirect to another page but in my case this is not possible because I don't have any page to redirect and my goal was to get an error 404.
Ideally a true error 404 would be better for allow google understand this url is really no more available and need to be removed from his index. Now I'm not sure if google will consider an error 410 or error 403 like an error 404.
Maybe it would be better to use a error 301 instead to error 410 and redirect to a fake inexistent page who will produce a true error 404 ???
have you any advices about this ??