Use QR Codes (Google API or QR Code Lib) anywhere in your blog, as a Widget, Shortcode, Tooltip or with a PHP function.
No. This plugin is based on OOP sytle which is not available in PHP4. Please upgrade your PHP installation.
Yes it does.
I don't know. Not tested yet.
PNG is the preferred one. If you're concerned about very old browser, use GIF instead. Or JPEG.
If you're on a webserver that disallows online connection from within php scripts, you should switch over to the QR Code Lib.
/qr-code-tag/data/ directory is not writeable. Please adjust
your permissions. See Changing File Permissions.
See Plugin Help (below Plugin settings in your WordPress administration area).
This is a PHP / WordPress problem. See Sudden empty / blank page for large posts with WordPress for problem description and solutions.
Google Chart API creates a different margin. I can't tell you why - ask Google.
You can use the Google ZXing online service
Because no one translated it yet. How about you? See Plugin Help for translation hints!