I get this in Firefox too.
The login is only on rare occasions as I log in for keeps, but I do notice it for the PM issue.
Ive mentioned it before and it the replies seemed to suggest it was not happening for all Firefox users.
Im using FF at work currently. Ill check how it reacts here.
Yep - same issues. Version 126.96.36.199
When selecting PM, or modifying a post, or login, detail only starts some point below requiring page or scroll down.