I have installed foswiki and made basic configuration changes (enabled/disabled plugins, change of patch etc.). Since that time I can see red error message on every window "No such theme PatternSkinTheme" and the banner with Foswiki's logo, "Jump" and "Search" textboxes is located in the end of the pages.

I tried to revert the configuration back, however the situation still persists. Does somebody know where might be the issue?
Thank you
So there were 2 issues: First issue was related with error message and the second with incorrect position of the banner.
First issue
The message disappeared after adding in /path/to/foswiki/lib/LocalSite.cfg following lines:
$Foswiki::cfg{JQueryPlugin}{Themes}{PatternSkinTheme}{Enabled} = 1;$Foswiki::cfg{JQueryPlugin}{Themes}{PatternSkinTheme}{Url} = $Foswiki::cfg{PubUrlPath}/$Foswiki::cfg{SystemWebName}/PatternSkinTheme/jquery-ui.css';Second issue
Update in file /path/to/foswiki/templates/foswiki.pattern.tmpl structure of the webpage. I removed
%TMPL:P{"topbar"}%from the definition like this... </div>%TMPL:P{"endsidebarwrapper"}%%TMPL:P{"topbar"}%%TMPL:P{"bottombar"}% ...and place it to
... %TMPL:DEF{"main"}%<div class="foswikiPage"><div id="patternScreen"> <div id="patternPageShadow">%TMPL:P{"topbar"}%%TMPL:P{"metanavigation"}% <div id="patternPage"> ...