Web site display issues in IE8

After upgrading to IE8, I notice our web site (www.dotnetideas.com) doesn’t look pretty anymore. One issue is the dropdown menus are blank. I searched the internet and found several solutions. I just used the easiest one. That is to add the following to your style sheet and page.

.IE8Fix  
{  
    z-index: 100;  
}

<DynamicMenuStyle CssClass="IE8Fix" />

Another issue I run into does not just happen in IE8, but also in FireFox. Our master page contains three columns. The left and right columns are set to float left and right. They are displayed nicely in IE7. But in IE8 and FireFox, the left column was squeezed when there is no content and the background image of the middle column was moved over to the far left. The solution to it is add the following line to the style sheet for the middle column

overflow:hidden;