It can't. The Lion kernel is x86-only and all of the PPC headers and framework APIs have been stripped out of the OS (and I think that with Mac OS 10.8, the kernel is going to be x64-only, so no more support for 32bit Intel machines even). There is no workaround for PPC code, aside from running Snow Leopard in a VM Client (which is doable, if you really, really need that file).From hearsay, I had that Rosetta could work under Lion, but I have no proof.
If you absolutely must run IE, try:I need IE, because I have an archive that was saved under .WAFF, that I need access to. Do you know any modern browsers than can read that?...
If you absolutely must run IE, try:
Installing Snow Leopard (with Rosetta) into Parallels 7 in Lion
[click on image to enlarge]