It's in either of these:
If you need something even more customized, the banner is output from the logo() function in the theme (qa-theme-base.php or qa-theme.php in your theme folder).
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask here, in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.