The form action (for Infinitydoes) is "/#cid_106". It should really be either "#cid_106" or "/contact#cid_106".
The effect is that the "/" is interpreted by the server as an absolute url which is the root (ie. the home page) and the "#cid_106" is treated as a (non-existent) named anchor.
This is a problem that has been
reported before.
I notice that your url does not have index.php in it, so you may be using some SEO plugin or even perhaps the "Use URL rewriting" option in Global Configuration.
Try turning that off and see what happens.