I added an external link in the Full Sitemap.

I use manual nav block in my header nav to put the external link.

When clicking from HOME (www.example.com) the external link opens

http://www.example.com/?cID=148 and correctly opens the link.

But when I open other pages (www.example.com/contact) the external link properly show up, however clicking on the external link in the header the link shows upwww.www.example.com/contact/?cID=148... and does nothing i.e stays on the same page.

This phenomena occurs in every page except the home have.

Anyone here know what the hell is going on??