Já bych to asi udělal:
<body style="text-align: center">
<div style="height: 420px; width: 420px; margin: auto"><!--cely-->
<div style="height: 60px; width: 300px; margin: auto; text-align: center; background-color: red">
a
</div>
<div style="height: 300px; width: 60px; margin: 0; float: left; text-align: center; background-color: blue">
b
</div>
<div style="height: 300px; width: 300px; float: left; margin: 0; text-align: center; background-color: green">
c
</div>
<div style="height: 300px; width: 60px; margin: 0; float: right; text-align: center; background-color: silver">
d
</div>
<div style="clear: both; height: 60px; width: 300px; margin: auto; text-align: center; background-color: yellow">
e
</div>
</div><!--cely-->
</body>a vznikne
Stačí u toho prostředka nastavit obtékání (left left right) a nemusí se pozicovat nic.