If you have built a website, fully customised it for IE 8 or IE 7 and think that re-designing your website keeping IE 9 standards in mind would take some time, then here is a quick tip which you can use in order to make your website (which works perfect in IE 8 & IE 7) to work well in IE 9 as well.
All you need to do is include this meta tag in your website's source within the header (or the <head>...</head> tags) if you want the browser to behave as IE 7 when it renders your website.
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />
Use this tag if you want the browser to behave as IE 8 when it renders your website.
<meta http-equiv="X-UA-Compatible" content="IE=8" />
You can use the two tags in conjunction as well. For more details about this, please check the post on MSDN.