URL redirect not working properly

[eluser]Unknown[/eluser]
Hi,

Let's say I have a url: www.my-site.com/index.php/admin

I have a simple form which on submit should go to 'clients/add'.

Instead I get something like this: www.my-site.com/index.php/admin/www.my-site.com/index.php/clients/add

I am sure it's a simple amateur problem, but still a problem... Could somebody tell me:

1. why is this request handled this way.
2. how can i fix it.

Thanks! | Sebastian.