diff --git a/config.php b/config.php
index a4d29c9..fc57dd5 100644
--- a/config.php
+++ b/config.php
@@ -1,7 +1,18 @@
 <?php
+## WARNING ##
+# ALWAYS make sure your `DATA_DIR` and `DATA_URL` (resp. IMAGES_) are
+# consistent. If you are using relative paths, it will be enforced by default.
+# If you are using absolute paths (ie. `MEDIA_BASE_DIR` is absolute), you will
+# have to make sure your web server serves `DATA_DIR` at `DATA_URL` (resp.
+# IMAGES_).
+#############
+
 define('THUMB_SIZE', 100);
 define('JPEG_QUALITY', '80');
-define('DATA_DIR', 'data');
-define('IMAGES_DIR', 'images');
+define('MEDIA_BASE_DIR', ''); # Useful whenever those should be absolute locations
+define('DATA_DIR', MEDIA_BASE_DIR . 'data');
+define('DATA_URL', DATA_DIR); # Used in urls, but not in filesystem paths
+define('IMAGES_DIR', MEDIA_BASE_DIR . 'images');
+define('IMAGES_URL', IMAGES_DIR); # Used in urls, but not in filesystem paths
 define('DATA_UMASK', 0002); # 0002: allow group to write for files created in data dir. change to 0022 to be more strict.
 ?>
diff --git a/functions.php b/functions.php
index 867bb49..8f568d6 100644
--- a/functions.php
+++ b/functions.php
@@ -28,7 +28,7 @@ function getPathInfo()
 if (! function_exists('getImageLink')) {
 function getImageLink($imageSimplePath)
 {
-	return $GLOBALS['rootUrl'].IMAGES_DIR.$imageSimplePath;
+	return $GLOBALS['rootUrl'].IMAGES_URL.$imageSimplePath;
 }
 }
 
@@ -36,11 +36,13 @@ if (! function_exists('getPreview')) {
 function getPreview($imgFile, $maxSize = THUMB_SIZE)
 {
 	# example: data/myalbum/100.mypic.jpg
-	$newImgFile = DATA_DIR."/".dirname($imgFile)."/".$maxSize.".".basename($imgFile);
-	
+	$origImgFile = IMAGES_DIR . $imgFile;
+	$basePath = dirname($imgFile)."/".$maxSize.".".basename($imgFile);
+	$newImgFile = DATA_DIR . "/" . $basePath;
+
 	# if the preview is a symlink, image is already good sized
 	if (is_link($newImgFile)) return $imgFile;
-	
+
 	if (! is_file($newImgFile))
 	{
 		# this tels the template to flush output after displaying previews
@@ -51,10 +53,10 @@ function getPreview($imgFile, $maxSize = THUMB_SIZE)
 
 		$ext = strtolower(substr($imgFile, -4));
 		if ($ext == ".jpg") {
-			$img = imagecreatefromjpeg($imgFile);
-			$exif = exif_read_data($imgFile);
+			$img = imagecreatefromjpeg($origImgFile);
+			$exif = exif_read_data($origImgFile);
 		} else {
-			$img = imagecreatefrompng($imgFile);
+			$img = imagecreatefrompng($origImgFile);
 		}
 		if ($img === false) return ""; #read error (wrong permission...)
 
@@ -96,25 +98,27 @@ function getPreview($imgFile, $maxSize = THUMB_SIZE)
 		} else {
 			imagepng($newImg, $newImgFile);
 		}
-		
+
 		imagedestroy($img);
 		imagedestroy($newImg);
 	}
 
-	return $newImgFile;
+	return $basePath;
 }
 }
 
 function getAlbumPreview($dir)
 {
-	$previewFile = DATA_DIR."/$dir/albumpreview";
+	$previewBase = "/$dir/albumpreview";
+	$previewFile = DATA_DIR . $previewBase;
+	$dirPath = IMAGES_DIR . "/$dir/";
 
 	if (is_file("$previewFile.jpg")) {
-		return "$previewFile.jpg";
+		return "$previewBase.jpg";
 	} else if (is_file("$previewFile.empty")) {
 		return "";
 	} else if (is_file("$previewFile.png")) {
-		return "$previewFile.png";
+		return "$previewBase.png";
 	} else {
 		# config to allow group writable files
 		umask(DATA_UMASK);
@@ -123,17 +127,18 @@ function getAlbumPreview($dir)
 			or die("Could not write in data dir. Please fix permissions.");
 
 		// no preview: look for a preview in current dir, write it, return it
-		foreach (scandir($dir) as $file) if ($file[0] != '.') {
+		foreach (scandir($dirPath) as $file) if ($file[0] != '.') {
 			$ext = strtolower(substr($file, -4));
 			if ($ext == ".jpg" or $ext == ".png") {
-				$thumb = getPreview("$dir/$file");
+				$thumbUrl = getPreview("$dir/$file");
+				$thumb = DATA_DIR . $thumbUrl;
 				copy($thumb, $previewFile.$ext);
-				return $previewFile.$ext;
-			} else if (is_dir("$dir/$file")) {
+				return $previewBase.$ext;
+			} else if (is_dir("$dirPath/$file")) {
 				$subPreview = getAlbumPreview("$dir/$file");
 				if ($subPreview) {
-					$myPreview = dirname($previewFile)."/".basename($subPreview);
-					copy($subPreview, $myPreview);
+					$myPreview = dirname($previewBase)."/".basename($subPreview);
+					copy(DATA_DIR . $subPreview, DATA_DIR . $myPreview);
 					return $myPreview;
 				}
 			}
diff --git a/index.php b/index.php
index e77be4e..602fac0 100644
--- a/index.php
+++ b/index.php
@@ -28,7 +28,6 @@ if (substr($rootUrl, -1) !== '/') $rootUrl.='/';  // add a trailing / to rootUrl
 
 require 'functions.php';
 
-
 // if url == http://localhost/photos/index.php/toto/titi, path_info == /toto/titi
 // if url == http://localhost/photos/index.php, path_info is not set
 // if url == http://localhost/photos/, path_info is not set
@@ -59,15 +58,23 @@ foreach (scandir($realDir) as $file) if ($file[0] != '.')
 {
 	if (is_dir("$realDir/$file"))
 	{
-		$folders[] = array( "name" => $file, "file" => "$realDir/$file", "link" => "$scriptUrl$simplePath/$file" );
+    $folders[] = array(
+      "name" => $file,
+      "file" => "$simplePath/$file",
+      "link" => "$scriptUrl$simplePath/$file");
 	}
 	else
 	{
 		$ext = strtolower(substr($file, -4));
 		if ($ext == ".jpg" or $ext == ".png") {
-			$imageFiles[] = array( "name" => $file, "file" => "$realDir/$file", "link" => getImageLink("$simplePath/$file") );
+      $imageFiles[] = array(
+        "name" => $file,
+        "file" => "$simplePath/$file",
+        "link" => getImageLink("$simplePath/$file"));
 		} else {
-			$otherFiles[] = array( "name" => $file, "link" => "$rootUrl$realDir/$file" );
+      $otherFiles[] = array(
+        "name" => $file,
+        "link" => "$rootUrl$realDir/$file");
 		}
 	}
 }
diff --git a/template.php b/template.php
index 28d5985..62536cf 100644
--- a/template.php
+++ b/template.php
@@ -64,7 +64,7 @@ a {
 		<div class="square"><div class="image_nopreview"><a href="<?= $folder["link"] ?>">■</a></div></div>
 		<div class="square"><div class="foldername_nopreview"> <a href="<?= $folder["link"] ?>"><?= $folder["name"] ?></a> </div></div>
 	<?php } else { ?>
-		<div class="square"><div class="image"> <a href="<?= $folder["link"] ?>"><img src="<?= $rootUrl.$preview ?>" /></a> </div></div>
+		<div class="square"><div class="image"> <a href="<?= $folder["link"] ?>"><img src="<?= $rootUrl.DATA_URL.$preview ?>" /></a> </div></div>
 		<div class="square"><div class="foldername"> <a href="<?= $folder["link"] ?>"><?= $folder["name"] ?></a> </div></div>
 		<?php if (isset($generating)) { ob_flush(); flush(); } ?>
 	<?php } ?>
@@ -74,7 +74,7 @@ a {
 
 <div id="images">
 <?php foreach ($imageFiles as $file) { ?>
-<?php $previewfile = $rootUrl.getPreview($file["file"]) ?>
+<?php $previewfile = $rootUrl . DATA_URL . getPreview($file["file"]) ?>
 	<div class="square"><div class="image imagepreview"><a href="<?= $file["link"] ?>"><img src="<?= $previewfile ?>" alt="<?= $file["name"] ?>" /></a></div><?php plugins_include("after_thumb.php") ?></div>
 	<?php if (isset($generating)) { ob_flush(); flush(); } ?>
 <?php } ?>