Salve ho un problema di compatibilità, su Fire Fox indenta correttamente su IE no,sapete aiutarmi??

questo il testo :
<p class="maiuscolo" style="text-align:justify">Laaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.</p>
il css:

p{margin:0 0 2em}
p.maiuscolo:first-letter {
float:left;
font: bold 100px/85px Georgia,"Times New Roman", Times,serif;
color: #DDD
}