diff --git a/crereader.lua b/crereader.lua
index b542334dd..39902edba 100644
--- a/crereader.lua
+++ b/crereader.lua
@@ -34,26 +34,37 @@ function CREReader:init()
 end
 -- inspect the zipfile content
 function CREReader:ZipContentExt(fname)
-	local outfile = "./data/zip_content"
-	local s = ""
-	os.execute("unzip ".."-l \""..fname.."\" > "..outfile)
+	local outfile, s = "./data/zip_content"
+	os.execute("unzip -l \""..fname.."\" > "..outfile)
 	local i = 1
 	if io.open(outfile,"r") then
 		for lines in io.lines(outfile) do 
 			if i == 4 then s = lines break else i = i + 1 end
 		end
 	end
-	-- return the extention
-	return string.lower(string.match(s, ".+%.([^.]+)"))
+	if s then -- return the extention
+		return string.lower(string.match(s, ".+%.([^.]+)") or "")
+	else
+		return nil
+	end
 end
 
+
 -- open a CREngine supported file and its settings store
 function CREReader:open(filename)
 	local ok
-	local file_type = string.lower(string.match(filename, ".+%.([^.]+)"))
+	local file_type = string.lower(string.match(filename, ".+%.([^.]+)") or "")
+	-- check zips for potential problems - wrong zip & wrong content
 	if file_type == "zip" then
 		file_type = self:ZipContentExt(filename)
 	end
+	if not file_type then
+		return false, "Error unzipping file. "
+	end
+	-- if the zip entry is not cre-document
+	if ext:getReader(file_type) ~= CREReader then
+		return false, "Zip contains improper content. "
+	end
 	-- these two format use the same css file
 	if file_type == "html" then
 		file_type = "htm"
@@ -63,10 +74,9 @@ function CREReader:open(filename)
 		file_type = "cr3"
 	end
 	local style_sheet = "./data/"..file_type..".css"
-	ok, self.doc = pcall(cre.openDocument, filename, style_sheet,
-						G_width, G_height)
+	ok, self.doc = pcall(cre.openDocument, filename, style_sheet, G_width, G_height)
 	if not ok then
-		return false, self.doc -- will contain error message
+		return false, "Error opening cre-document. " -- self.doc, will contain error message
 	end
 	self.doc:setDefaultInterlineSpace(self.line_space_percent)
 	return true
diff --git a/reader.lua b/reader.lua
index 94b36b173..4f6be8eb7 100755
--- a/reader.lua
+++ b/reader.lua
@@ -53,7 +53,7 @@ function openFile(filename)
 			G_reader_settings:saveSetting("lastfile", filename)
 			return reader:inputLoop()
 		else
-			InfoMessage:show("Error opening document.", 0)
+			InfoMessage:show(err or "Error opening document.", 0)
 			util.sleep(2)
 		end
 	end
diff --git a/unireader.lua b/unireader.lua
index 632655875..7889fa22a 100644
--- a/unireader.lua
+++ b/unireader.lua
@@ -2007,18 +2007,18 @@ function UniReader:addAllCommands()
 			(keydef.keycode == KEY_PGBCK or keydef.keycode == KEY_LPGBCK)
 			and unireader:prevView() or unireader:nextView())
 		end)
-	self.commands:addGroup(MOD_SHIFT.."< >",{
-		Keydef:new(KEY_PGBCK,MOD_SHIFT),Keydef:new(KEY_PGFWD,MOD_SHIFT),
-		Keydef:new(KEY_LPGBCK,MOD_SHIFT),Keydef:new(KEY_LPGFWD,MOD_SHIFT)},
+	self.commands:addGroup(MOD_ALT.."< >",{
+		Keydef:new(KEY_PGBCK,MOD_ALT),Keydef:new(KEY_PGFWD,MOD_ALT),
+		Keydef:new(KEY_LPGBCK,MOD_ALT),Keydef:new(KEY_LPGFWD,MOD_ALT)},
 		"zoom out/in ".. self.step_manual_zoom .."% ",
 		function(unireader,keydef)
 			local is_zoom_out = (keydef.keycode == KEY_PGBCK or keydef.keycode == KEY_LPGBCK)
 			unireader:setGlobalZoom(unireader.globalzoom_orig * (1 + (is_zoom_out and -1 or 1)*unireader.step_manual_zoom/100))
 		end)
 	-- NuPogodi, 03.09.12: make zoom step user-configurable
-	self.commands:addGroup(MOD_ALT.."< >",{
-		Keydef:new(KEY_PGBCK,MOD_ALT),Keydef:new(KEY_PGFWD,MOD_ALT),
-		Keydef:new(KEY_LPGBCK,MOD_ALT),Keydef:new(KEY_LPGFWD,MOD_ALT)},
+	self.commands:addGroup(MOD_SHIFT.."< >",{
+		Keydef:new(KEY_PGBCK,MOD_SHIFT),Keydef:new(KEY_PGFWD,MOD_SHIFT),
+		Keydef:new(KEY_LPGBCK,MOD_SHIFT),Keydef:new(KEY_LPGFWD,MOD_SHIFT)},
 		"decrease/increase zoom step",
 		function(unireader,keydef)
 			if keydef.keycode == KEY_PGFWD or keydef.keycode == KEY_LPGFWD then
@@ -2593,6 +2593,10 @@ function UniReader:addAllCommands()
 			local minstep = 1
 			if keydef.keycode == KEY_FW_RIGHT then
 				unireader.shift_x = unireader.shift_x * 2
+				if unireader.shift_x >= G_width then
+					unireader.shift_x = G_width
+					showInfoMsgWithDelay("Maximum X-panning step is "..G_width..". ", 2000, 1)
+				end
 				self.settings:saveSetting("shift_x", self.shift_x)
 				--showInfoMsgWithDelay("New X-panning step is "..unireader.shift_x..". ", 2000, 1)
 			else
@@ -2612,6 +2616,10 @@ function UniReader:addAllCommands()
 			local minstep = 1
 			if keydef.keycode == KEY_FW_UP then
 				unireader.shift_y = unireader.shift_y * 2
+				if unireader.shift_y >= G_height then
+					unireader.shift_y = G_height
+					showInfoMsgWithDelay("Maximum Y-panning step is "..G_height..". ", 2000, 1)
+				end
 				self.settings:saveSetting("shift_y", self.shift_y)
 				--showInfoMsgWithDelay("New Y-panning step is "..unireader.shift_y..". ", 2000, 1)
 			else