Thank you all for your help. I didn't edit the html file manually nor did I edit the $:/boot/boot.css tiddler.
I Could not find the reason for the error, so in the end. I rolled back to a backup and imported my tiddelers (without system tid) made since that point in time. @Hubert Oh that is so nice. I really like the clean dark look. thanks (and sorry but now I know that I find the standard password prompt really ugly) -- You received this message because you are subscribed to the Google Groups "TiddlyWiki" group. To unsubscribe from this group and stop receiving emails from it, send an email to tiddlywiki+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/tiddlywiki/5305bca9-cc8c-4835-b789-f7ca59dd884c%40googlegroups.com.