Wordpress .entry-content class will not properly align with sidebar

I've encountered another silly problem while trying to enable sidebar on pages on Wordpress Twentyeleven theme.

I've given my .entry-content class:

.entry-content {float:left !important;width:648px !important;}

excuse me for those !importants, I just don't dare to edit the default style.css...

Now I've added

<?php get_sidebar(); ?>

By the end of page.php, just above the get_footer stuff... and sidebar apparently disp开发者_C百科lays UNDER my .entry-content, on the right hand side....

I've trying giving the sidebar a float:right, but it still won't float.

Here is an example.

Inside <div id="main"> you have a <div id="primary">. Set a width on the primary div and this is solved.

Like this: #primary {width:400px;}