It seems like your stylesheet is non-existent? stylesheet.css ??

If this is a new install??????? ...... then I recommend copying the original (downloaded) stylesheet.css to the includes/templates/YOURTEMPLATE/css directory...... Be careful not to overwrite the existing file..... just rename the existing and replace with the original.

same goes for includes/configure.php...... replace with original but be careful not to overwrite.

NEVER overwrite files... always rename the file you're about to overwrite so that if something goes wrong you still have the original/previous version.