The barcode named Code128 has the ability to encode all ASCII characters with their case.
Print this page and scan the code .. :-)
Displaying a Code128 barcode is as simple as placing a <img>-tag on your website.
The following values in the <img>'s src attribute control the display:
<img src="/isapi/barcode_isapi.dll?hash=......" border="0">
hash= value to display as Code128 barcode
direction= v or h // V for vertical, H for horizontal
height= numerical value // defines the height of a code element, play with it to find your best value
href=, optional, referer host if user blocked referer logging
Addidionally, you can deploy an isapi_barcode.ini-file to your Windows directory to define good referers. This allows you to prevent using the barcode generator from other websites. If you don't care about the load on your webserver that this unfriendly usage could generate, you don't need it.
The above mentioned href= value is coded in the source, so it is visible. Any malicious website can of course hardcode this to a value that is your webhost. So, this is no perfect protection at all. However, the href= comes into play only, if the browser does deliver no or an empty referer.
A sample of this ini-file and the source of the example page is provided in the retail.zip.