I know. But I've had the experience that, especially with sites that need session cookies or proper referrers, wget will save the error page with the same name as the file that should be downloaded.
the above command downloaded 44K size of rar file, but I could not open the rar file , the error message while opening is file is damaged or incorrect format.
please suggest me correct syntax, I am unable to open rar file so I can't see what is the message in the file.
I used user name and password so i don't think the problem is with user name and password.
Also, you can get a hint at the contents using the man file (Linux) utility, if available. If the result is "HTML document text" (or something alike) you didn't download an archive but a webpage.
The op already stated they cannot open it. It is a partial download of a rar file, as the op said. HTML error messages are not 44k in size. It is a partial download as the posted.
I believe he is trying to open it using RAR software (whatever that's called on Ubuntu).
If the server returned an error (i.e. 404 or authentication error) it would likely be the same HTML page you would see in a web browser. That could be any size.
Just for fun I tried the download like the OP. It is an HTML "error message", 44k in size, telling the user that there's no valid login and that you should provide credentials (because there's no session cookie).
@LinuxLearner: the --user and --password options only work with FTP or HTTP Basic Authentication, but not with Form-based (eg: input boxes) / session cookie authentication. For that you'll have to resort to screen-scraping, or create a file with a valid cookie, and supply that via the --load-cookies parameter.