For some reason, dropcaps that look OK in Sigil don't look OK in the compiled .mobi file and the dropcaps code that Amazon recommends in the
Publishing Guidelines doesn't work in epubs.
Amazon recommends the following code, which works fine on my K3 with the default fonts, if I compile the .epub with KindleGen.
Code:
span.dropcaps
{
font-weight:normal;
font-size:320%;
float:left;
margin-top:-0.3225em;
margin-bottom:-0.3245em;
}