as stated by others, this error means there is output to the page.
Inspect the error closer and it says:
output started at /home/galler11/public_html/store/Connections/localhost.php:3
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.