problem of input button.

I use wp3.0.1 and buddypress newest version.
I add some input button in the index.php of the BP theme.
<input type="submit" value="name" onclick="sub('name')"> and set it to the index.php.
such as first, the home page is http://localhost/wordpress/
When I click the input button ,the url change to :’http://localhost/wordpress/index.php’
And it show: ‘Sorry, no posts matched your criteria.’ and the index.php screen show is not the first page, but a page like login statement page.
I copy the url ‘http://localhost/wordpress/index.php’ to my new ie windows and open it, It also shows the original home page.
What is the reason, how to solve? Thanks.