diff --git a/build b/build
index c763b8c..8f58e88 100755
--- a/build
+++ b/build
@@ -14,9 +14,12 @@ else
     ./mdbook build -d public
 fi
 
+cp -R static/* public/
+
+# Work around some print.html bugs.
+sed -i "s/\(href\|src\)=\"[[:alnum:]\-]*\/\//\1=\"\//g" public/print.html
+
 ./move_html_to_dir public/
 
 # Make checkboxes editable, just in case the user wants to keep their own checklist.
 find public/ -name "*.html" -type f -exec sed -i 's/input disabled=""/input/g' {} +
-
-cp -R static/* public/
diff --git a/content/ardupilot/ardupilot-setup-checklist.md b/content/ardupilot/ardupilot-setup-checklist.md
index 832b42e..d43f8a4 100644
--- a/content/ardupilot/ardupilot-setup-checklist.md
+++ b/content/ardupilot/ardupilot-setup-checklist.md
@@ -13,7 +13,7 @@ It's called Parachute, and you can download it here:
 
 
 ## Building ArduPilot
-See [Building ArduPilot](/ardupilot/building-ardupilot) for instructions on how to build the latest version.
+See [Building ArduPilot](/ardupilot/building-ardupilot.html) for instructions on how to build the latest version.
 
 
 ## Hardware setup
@@ -98,7 +98,7 @@ The values in this section are specific to the Omnibus F4, but the settings aren
 
 ## Recommended settings.
 
-See the [recommended settings](/ardupilot/ardupilot-recommended-settings) page for other recommended defaults.
+See the [recommended settings](/ardupilot/ardupilot-recommended-settings.html) page for other recommended defaults.
 
 ## In the field
 - [ ] Run an autotune.
diff --git a/content/ardupilot/tecs-tuning-calculator.md b/content/ardupilot/tecs-tuning-calculator.md
index 2b6a4de..c2226a7 100644
--- a/content/ardupilot/tecs-tuning-calculator.md
+++ b/content/ardupilot/tecs-tuning-calculator.md
@@ -1,6 +1,6 @@
 # TECS tuning calculator
 
-To use this calculator, first follow the steps in [Tuning the TECS](/ardupilot/tuning-the-tecs).
+To use this calculator, first follow the steps in [Tuning the TECS](/ardupilot/tuning-the-tecs.html).
 
 <script>
     function kmhToMs(kmh) { return Math.round(kmh / 3.6); }
diff --git a/content/ardupilot/tuning-the-tecs.md b/content/ardupilot/tuning-the-tecs.md
index bd6075b..4925b11 100644
--- a/content/ardupilot/tuning-the-tecs.md
+++ b/content/ardupilot/tuning-the-tecs.md
@@ -62,7 +62,7 @@ You're done with this step.
 ### On the bench
 After you have the above measurements, you're ready to tune things. You can use the automatic calculator:
 
-### [TECS tuning calculator](/ardupilot/tecs-tuning-calculator)
+### [TECS tuning calculator](/ardupilot/tecs-tuning-calculator.html)
 
 Otherwise, you can do things manually, following the steps below, but you should really use the calculator instead.
 
diff --git a/joplinexport b/joplinexport
index 795f9db..6a83fc3 100755
--- a/joplinexport
+++ b/joplinexport
@@ -157,7 +157,9 @@ class JoplinExporter:
         def replacement(match):
             item_id = match.group(1)
             new_url = self.get_note_url_by_id(item_id)
-            if not new_url:
+            if new_url:
+                new_url += ".html"
+            else:
                 new_url = self.get_resource_url_by_id(item_id)
                 if not new_url:
                     new_url = item_id
diff --git a/move_html_to_dir b/move_html_to_dir
index 98eadbe..3e8298e 100755
--- a/move_html_to_dir
+++ b/move_html_to_dir
@@ -6,6 +6,54 @@ import re
 import sys
 from pathlib import Path
 from typing import Dict
+from typing import List
+
+
+def get_safe_path(root: Path, candidate: Path) -> Path:
+    """
+    Return the safe path between two paths.
+
+    This function checks that a candidate path is under the given root. If it is, it
+    returns the candidate path unchanged. If not, it returns the topmost ancestor that
+    is not part of the root, as the relative path.
+
+    For illustration, some inputs and outputs:
+    >>> get_safe_path("/var/www/mydocs", "/var/www/mydocs/foo")
+    "/var/www/mydocs/foo"
+
+    >>> get_safe_path("/var/www/mydocs", "/var/www/foo")
+    "/var/www/mydocs/foo"
+
+    >>> get_safe_path("/var/www/mydocs", "/foo")
+    "/var/www/mydocs/foo"
+    """
+    if not root.is_absolute() and candidate.is_absolute():
+        raise ValueError("Both paths must be absolute")
+
+    try:
+        # If the candidate is under the root, we're done.
+        candidate.relative_to(root)
+        return candidate
+    except ValueError:
+        pass
+
+    # Otherwise, look for the first point of divergence from the root.
+    for counter, part in enumerate(root.parts):
+        if counter >= len(candidate.parts):
+            parts: List[str] = []
+            break
+
+        if part != candidate.parts[counter]:
+            # Everything past that is what we need.
+            parts = candidate.parts[counter:]
+            break
+
+    outpath = root
+    # Tack the discovered parts onto the root.
+    for part in parts:
+        outpath /= part
+
+    return outpath
 
 
 def convert_relative_to_absolute(path: Path):
@@ -21,7 +69,12 @@ def convert_relative_to_absolute(path: Path):
     def replace_wrapper(filename: Path):
         def replace_link(match: re.Match) -> str:
             property, text, suffix = match.groups()
-            if "://" in text or text == "/" or text.startswith("#"):
+            if (
+                "://" in text
+                or text == "/"
+                or text.startswith("#")
+                or text.startswith("mailto")
+            ):
                 # Not a valid filename, return it.
                 return f"{property}{text}{suffix}"
 
@@ -30,6 +83,7 @@ def convert_relative_to_absolute(path: Path):
             else:
                 filepath = (filename.parent / text).resolve()
 
+            filepath = get_safe_path(path, filepath)
             if not filepath.exists():
                 # Not a valid filename, return it.
                 sys.exit(f"Possible broken link in {filename}: {text}")
@@ -87,6 +141,7 @@ def replace_links(path: Path, replacements: Dict[str, str]):
 
 
 def main(path: Path):
+    path = path.resolve()
     convert_relative_to_absolute(path)
 
     replacements: Dict[str, str] = {}