Internet Explorer ignore my css

This is not a WordPress question but a general HTML / CSS question, as such you will likely get better answers elsewhere (StackOverflow).

If you add this to your meta tags inside the head tag:


<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />

This will render the page like IE7.

However I don’t recommend this; if you are developing a theme really you should focus on using newer HTML5 doc types / coding practices and fixing the problems there.

You might find Microsoft’s http://modern.ie website helpful in identifying and tracking other issues.