I'll follow Curt's theoretical grounding (unless someone beats me to it).
In all honesty, I haven't thought deeply about the "performativity of
code," at least not worded in quite this way. But, when I read Arns'
"Program code is characterized by the fact that here 'saying' coincides
with 'doing,'" I felt myself nodding my head in agreement.
Web code is a set of instructions that a browser interprets and a
viewer/user experiences. The artist authors the directions (providing the
"saying") and, following Curt's summary of Barthes, Austin, and Derrida:
the viewer/user collaborates with the browser to execute the doing.
What I enjoy about the inherent set of directions--either showing up as the
code itself or as an implicit part of a web project--is the historical
connection that can be drawn between web projects and conceptual art works
that predate the web.
I feel like there's more to write but I don't want to ramble. Not yet
anyway. But if someone else feels like this is making sense, maybe there's
a connection that can be explored between how performativity is expressed
through "code" (social, written, or otherwise) for a pre-web conceptual
work and a contemporary new media project.