I have a web page which includes a basic content. I can chance its format but it is PHP now. I want to send this data to one of the serial ports of my computer (as a visitor
There is a library for PHP that supports writing to serial port.
See here.
More:
http://php.net/manual/en/function.fopen.php#20935
See this question for more discussion: How to Read RS232 Serial Port in PHP like this QBasic Program
Update:
To do this on windows see this tutorial: http://blog.950buy.com/article/php-use-rs232-serial-communication-to-send-file/
Also this question: Serial comm with PHP on Windows