How to create custom permalink?

Hi there,

I was wondering how I can create a custom permalink like the example below?:

http://www.websiteurl.com/site/index?pid=

Where the ‘index?pid=’ is similar to the default permalink ‘?p-‘ (displayed at the end of the URL).

Is there any way to do this? I’d prefer the word ‘index’ before the ‘pid=’ instead of it looking like ‘/?p=’, and I’d like to change the ‘?p=’ to ‘?pid=’ (where ‘pid’ means page id, which makes more sense to me).

I have tried doing this on the permalinks setting page on my wordpress website, where i put this in the text box next to my URL on the custom option (of the radio button form): ‘/index?’ – but this didnt work, and the result was this:

http://www.websiteurl.com/site/home

Where ‘home’ was the page name.

Thanks in advance for any replies!.