This may be because the site is instructing the browser to open them in a new tab (I know, it's a big usability issue, but the web is still young...). Can you try it on other browsers and see what happens? If the same happens, yes, it's probably the site that's telling the browser to open the link in another tab.

If you want to eliminate that behavior, and be in full control of where the links open (middle click to open in new tab, left click to open in the same tab - as it should be), I suggest you install an extension like Tab Mix Plus, which, among other things (many things, it's an absolutely phenomenal extension) will let you configure "links that open in a new window" to open on the current tab.

Your plugins list shows outdated plugin(s) with known security and stability risks.

• Next Generation Java Plug-in 1.6.0_17 for Mozilla browsers
• Shockwave Flash 10.1 r53

Update the Java plugin to the latest version.

• http://java.sun.com/javase/downloads/index.jsp#jdk (you need JRE)

Update the Flash plugin to the latest version.

• http://www.adobe.com/software/flash/about/