fixes about the dropdown menu and image links

Hello,

I started using your template and I noticed 2 issues: 

* When there are many hosts listed in the dropdown menu, it is not possible to select hosts in bottom of the list. So I just add some css rules to restrict the size of the dropdown menu and display a scrollbar if needed.

* Using some browsers, the image links rewrited by javascript are broken. So I just improve the regex to fix this issue.

Regards