i will answer this one for you.
for the WEB, the easiest fonts to read are san serifs.....i.e arial, verdana.
now from reading TONS of stuff, being a webdesigner and working on sites, my personal opinionis this.
for body copy, the most effective and eye pleasing font is: arial, size 2 (i use dreamweaver, so it has "font families")
typefaces such as times,(serifs) are best left for print...they look like crap on a site and are so hard to read....