Same way this site does, MSN isnt doing anything special or tricky to do that
in fact when I blow up my text alot of their text with imagery in the background starts to break apart.
It comes down to good html layout basics. That is why tables were so great to use back in the day, they were very expandable elements that kept your information organanized. Keep things on your site from overlapping, use more simple structures and your site will expand like that as well.
If you have to fix a site to do that which already exists, take a look at the images it uses and how it lines up. Imagery becomes impossible to line up once users start boucing their text sizes around
