HTML Character Encoding

[eluser]adrian westlake[/eluser]
I am working with another company to exhange data by firing off URLS passing in information in the query string (or segments in CI of course). They are encoding the query string so that characters like ampersands etc can be passed accross safely. However, on testing I found that if I pass something like

Code:

http://localhost/admin/test/this&26that

My browser displays

Code:

The URI you submitted has disallowed characters

Why is this happening? Surely the urldecode() method is being passed somewhere to decode this, so why is it unsafe to pass these characters around encoded?


Adrian