Hi,
I design website in asp.net but I have open source script for a website on PHP. I would like to edit so kindly tell me which software is used in php for webdesigning and provide it download link.

Greetings,

Most people just use a plain old text editor, so:

Notepad (although it does not like unix line ends)
WordPad

would work, but you may find:

TextPad
Notepad++

or some other text editor more to your liking.