I don't get it, because I care a lot about readability myself, and to me, dark blue on light grey is one of the most readable combinations. (Black text is better, but not significantly.)
Does anybody know why this should be so for some people, and how many it might affect?
Update: one of my readers wrote:
Now I know that you don't set a specific font size (I should have checked the source) I increased the font size in my browser and the text became quite readable. This has highlighted a problem I never knew existed in Google Chrome. Although the default font size was set to 16pt, which should be bigger than I prefer, the font was actually rendered at 8 or 9 points, which is what made it difficult to read.
Indeed GC makes very tiny text.
And most text can be enlarged in the browser, which has enormous influence on readability.
(And again I'll mention "Readable app" for easier reading on the web.)