Gmail gets a JavaScript facelift: As one small example, one team member reverse-engineered jscript.dll to figure out how its GC algorithm worked, and was horrified to find that it had hard-coded, arbitrary limits on how many objects could be allocated before a GC would occur. This led to an insane amount of effort optimizing the code to reduce the number of allocations in core code paths. [More good info in the article and links.]
Source: Ajaxian
Source: Ajaxian