There are three different doctypes: Frameset, Transitional and Strict. Strict is not yet the most used doctype but the one that serious web designers and professionals use. Many old codes won't work in Strict and among them the "target="blank" which is one of the few codes that can't be replaced with a similar css-code. The solution to this problem is to use a simple java script to open your links in new windows.
1. First you write down this code in a document which you name "script.js".
location=yes,directories=yes,fullscreen=no,titlebar=yes,hotkeys=yes,status=yes,scrollbars
=yes,resizable=yes'); }
2. Put this code in every document where you will use the link-script.
3. Finally this is how you from now on should write out links that should be opened in new windows.