a simple question about float property in IE

so here’s a simple question i just can’t answer:

i want my sidebar to float to the right of my content, using css. here’s the code i use:

#sidebar {
padding: 265px 0 0 0px;
margin-left: 750px;
font-size: 18px;
width: 155px;

}

#content {
float: left;
padding-left: 157px;
margin: 0px;
width: 540px;

}

works great in every browser i’ve checked except IE, where the sidebar appears *below* the content, rather than to the right.

what am i doing wrong?

thanks!