First off, 'float' is pretty well supported, even on IE. When validating the HTML on you website, I am getting 43 errors (wont really be that many). Correct those and see if it fixes the problem. Earlier versions of IE (<= 7) are not as friendly to slightly invalid markup as IE8, chrome, firefox, etc...
Second, if you are really just trying to display block elements inline, 'display:inline-block' is the easiest way. Contrary to popular belief, this is supported on IE7 & 8. Here is the css for cross browser support:
.inline-element {
display:-moz-inline-stack;
display:inline-block;
zoom:1;
*display:inline;
}