Hyperlink in Navigation

Hi There,

I thought I had a rather simple issue to implement but it seems to be more complicated:

I have been asked to put a link into our SF navigation to our Sharepoint. We have a list there for improvement suggestions by our users. I should put a link to this list in the navigation.
I tried to create a web tab, but at the end, i get the error that Sharepoint does not allow the connection (I guess iframes are blocked).
The only thing i need is a hyperlink, I dont need this to be embedded. It should open a new tab. I doubt this is impossible, yet i cannot find how to implement this.
any help is much appreciated!