If you want the two .block divs on the same row what I would do is not do it in pixels but with %'s.
For example what I would do is this:
Give your div that you want on the right an id of right and the one that you want on the left an id of left:
<div class="container">
<div class="block" id="right">content...</div>
<div class="block" id="left">content...</div>
</div>
Then I would style it with
<style>
.container{width:1000px; margin:0px auto;}
.block{width:48%;height:500px;display:inline;}
#left{float:left;}
#right{float:right;}
</style>
You can play around with the exact width percent to get it to your standards.