The Idle Theory website has gradually expanded since its inception on 1998, and now almost fills the 15 MB permitted. Adding new essays now begins to require that old essays be removed or contracted. And so some of the older essays will begin to be replaced.
Some of the essays - e.g. Easy Meat - very arguably have nothing to do with Idle Theory at all.
The same is true of the Orbital Siphon. However, since its publication in 2005, the siphon has become a subject of interest in the astronautical/space elevator community, so I will probably keep it.
The download facility, whereby the entire website can be downloaded as a zip file, may also be superfluous. People who become interested in Idle Theory seem to just visit it repeatedly. It probably doesn't matter to internet users with fast connections where the website is to be found.
The formal content of Idle Theory hasn't really changed much over 10 years, and has largely been a process of expanding upon ideas expressed earlier. But there are changes of emphasis which almost amount to changes of mind. For example, Idle Theory as an economic/political has generally been strongly egalitarian. But I've now shifted to thinking that while a general equality of idleness is a desirable ideal, it is not essential. Nor is it practically achievable. Future essays are likely to reflect this shift in thinking, and essays like Ship of Fools now seem to overstate the case for equality, while newer essays like Concerning Equality and Inequity Theory reflect my current thinking.