diff --git a/app.py b/app.py
index abf0e80..aadc83e 100644
--- a/app.py
+++ b/app.py
@@ -210,6 +210,13 @@ class Page(BaseModel):
         return PagePropertyDict(self)
     def is_editable(self):
         return not self.is_locked
+
+    def can_edit(self, user):
+        if self.is_locked:
+            return user.id == self.owner.id
+        return True
+    def is_owned_by(self, user):
+        return user.id == self.owner.id
             
 
 class PageText(BaseModel):
@@ -508,12 +515,16 @@ def error_404(body):
 def error_403(body):
     return render_template('forbidden.html'), 403
 
-@app.errorhandler(500)
+@app.errorhandler(400)
 def error_400(body):
     return render_template('badrequest.html'), 400
 
+@app.errorhandler(500)
+def error_500(body):
+    return render_template('internalservererror.html'), 500
+
 # Middle point during page editing.
-def savepoint(form, is_preview=False, pageid=None):
+def savepoint(form, is_preview=False, pageobj=None):
     if is_preview:
         preview = md(form['text'], math='enablemath' in form)
     else:
@@ -522,7 +533,7 @@ def savepoint(form, is_preview=False, pageid=None):
     pl_js_info['editing'] = dict(
         original_text = None, # TODO
         preview_text = form['text'],
-        page_id = pageid
+        page_id = pageobj.id if pageobj else None
     )
     return render_template(
         'edit.html',
@@ -531,11 +542,15 @@ def savepoint(form, is_preview=False, pageid=None):
         pl_text=form['text'],
         pl_tags=form['tags'],
         pl_enablemath='enablemath' in form,
+        pl_is_locked='lockpage' in form,
+        pl_owner_is_current_user=pageobj.is_owned_by(current_user) if pageobj else True,
         preview=preview,
-        pl_js_info=pl_js_info
+        pl_js_info=pl_js_info,
+        pl_readonly=not pageobj.can_edit(current_user) if pageobj else False
     )
 
 @app.route('/create/', methods=['GET', 'POST'])
+@login_required
 def create():
     if request.method == 'POST':
         if request.form.get('preview'):
@@ -559,7 +574,9 @@ def create():
                 title=request.form['title'],
                 is_redirect=False,
                 touched=datetime.datetime.now(),
-                is_math_enabled='enablemath' in request.form
+                owner=current_user,
+                is_math_enabled='enablemath' in request.form,
+                is_locked = 'lockpage' in request.form
             )
             p.change_tags(p_tags)
         except IntegrityError as e:
@@ -567,7 +584,7 @@ def create():
             return savepoint(request.form)
         pr = PageRevision.create(
             page=p,
-            user_id=0,
+            user_id=p.owner.id,
             comment='',
             textref=PageText.create_content(request.form['text']),
             pub_date=datetime.datetime.now(),
@@ -575,37 +592,49 @@ def create():
         )
         PageLink.parse_links(p, request.form['text'])
         return redirect(p.get_url())
-    return render_template('edit.html', pl_url=request.args.get('url'))
+    return savepoint({
+        "url": request.args.get("url"),
+        "title": "",
+        "text": "",
+        "tags": ""
+    })
 
 @app.route('/edit/<int:id>/', methods=['GET', 'POST'])
+@login_required
 def edit(id):
     p = Page[id]
     if request.method == 'POST':
+        # check if page is locked first!
+        if not p.can_edit(current_user):
+            flash('You are trying to edit a locked page!')
+            abort(403)
+
         if request.form.get('preview'):
-            return savepoint(request.form, is_preview=True, pageid=id)
+            return savepoint(request.form, is_preview=True, pageobj=p)
         p_url = request.form['url'] or None
         if p_url:
             if not is_valid_url(p_url):
                 flash('Invalid URL. Valid URLs contain only letters, numbers and hyphens.')
-                return savepoint(request.form, pageid=id)
+                return savepoint(request.form, pageobj=p)
             elif not is_url_available(p_url) and p_url != p.url:
                 flash('This URL is not available.')
-                return savepoint(request.form, pageid=id)
+                return savepoint(request.form, pageobj=p)
         p_tags = [x.strip().lower().replace(' ', '-').replace('_', '-').lstrip('#')
             for x in request.form.get('tags', '').split(',')]
         p_tags = [x for x in p_tags if x]
         if any(not re.fullmatch(SLUG_RE, x) for x in p_tags):
             flash('Invalid tags text. Tags contain only letters, numbers and hyphens, and are separated by comma.')
-            return savepoint(request.form, pageid=id)
+            return savepoint(request.form, pageobj=p)
         p.url = p_url
         p.title = request.form['title']
         p.touched = datetime.datetime.now()
         p.is_math_enabled = 'enablemath' in request.form
+        p.is_locked = 'lockpage' in request.form
         p.save()
         p.change_tags(p_tags)
         pr = PageRevision.create(
             page=p,
-            user_id=0,
+            user_id=current_user.id,
             comment='',
             textref=PageText.create_content(request.form['text']),
             pub_date=datetime.datetime.now(),
@@ -613,22 +642,19 @@ def edit(id):
         )
         PageLink.parse_links(p, request.form['text'])
         return redirect(p.get_url())
-    pl_js_info = dict()
-    pl_js_info['editing'] = dict(
-        original_text = None, # TODO
-        preview_text = None,
-        page_id = id
-    )
     
-    return render_template(
-        'edit.html',
-        pl_url=p.url,
-        pl_title=p.title,
-        pl_text=p.latest.text,
-        pl_tags=','.join(x.name for x in p.tags),
-        pl_js_info=pl_js_info,
-        pl_enablemath = p.is_math_enabled
-    )
+    form = {
+        "url": p.url,
+        "title": p.title,
+        "text": p.latest.text,
+        "tags": ','.join(x.name for x in p.tags)
+    }
+    if p.is_math_enabled:
+        form["enablemath"] = "1"
+    if p.is_locked:
+        form["lockpage"] = "1"
+    
+    return savepoint(form, pageobj=p)
 
 @app.route("/__sync_start")
 def __sync_start():
@@ -805,6 +831,8 @@ def theme_switch():
 
 @app.route('/accounts/login/', methods=['GET','POST'])
 def accounts_login():
+    if current_user.is_authenticated:
+        return redirect(request.args.get('next', '/'))
     if request.method == 'POST':
         try:
             username = request.form['username']
@@ -826,8 +854,6 @@ def accounts_login():
 
 @app.route('/accounts/register/', methods=['GET','POST'])
 def accounts_register():
-    if current_user.is_authenticated:
-        return redirect(request.args.get('next', '/'))
     if request.method == 'POST':
         username = request.form['username']
         password = request.form['password']
@@ -980,7 +1006,7 @@ class Importer(object):
 
                     rev = PageRevision.create(
                         page = p,
-                        user = self.owner.id,
+                        user_id = self.owner.id,
                         textref = textref,
                         comment = revobj.get('comment'),
                         pub_date = datetime.datetime.fromtimestamp(revobj['timestamp']),
diff --git a/i18n/salvi.en.json b/i18n/salvi.en.json
index c33dab1..2640b81 100644
--- a/i18n/salvi.en.json
+++ b/i18n/salvi.en.json
@@ -54,6 +54,7 @@
         "privacy-policy": "Privacy Policy",
         "already-have-account": "Already have an account?",
         "logged-in-as": "Logged in as",
-        "not-logged-in": "Not logged in"
+        "not-logged-in": "Not logged in",
+        "owner": "Owner"
     }
 }
\ No newline at end of file
diff --git a/i18n/salvi.it.json b/i18n/salvi.it.json
index a7b061a..6f7614e 100644
--- a/i18n/salvi.it.json
+++ b/i18n/salvi.it.json
@@ -45,6 +45,7 @@
         "notes-count-with-url": "Numero di note con URL impostato",
         "revision-count": "Numero di revisioni",
         "revision-count-per-page": "Media di revisioni per pagina",
-        "remember-me-for": "Ricordami per"
+        "remember-me-for": "Ricordami per",
+        "owner": "Proprietario"
     }
 }
\ No newline at end of file
diff --git a/templates/base.html b/templates/base.html
index 05b2850..6192923 100644
--- a/templates/base.html
+++ b/templates/base.html
@@ -45,7 +45,13 @@
     </ul>
     <div class="footer">
       <div class="footer-copyright">&copy; 2020–2023 Sakuragasaki46.</div>
-      <div class="footer-loggedinas">{% if current_user %}{{ T('logged-in-as') }}: <strong>{{ current_user.username }}</strong>{% else %}{{ T('not-logged-in') }}{% endif %}</div>
+      <div class="footer-loggedinas">
+        {% if current_user.is_authenticated %}
+        {{ T('logged-in-as') }}: <strong>{{ current_user.username }}</strong>
+        {% else %}
+        {{ T('not-logged-in') }}. <a href="/accounts/login">{{ T("login") }}</a>
+        {% endif %}
+      </div>
       <div class="footer-actions" id="page-actions">{% block actions %}{% endblock %}</div>
       <div class="footer-versions">{{app_name}} version {{app_version}}</div>
     </div>
diff --git a/templates/edit.html b/templates/edit.html
index 8440b28..0439228 100644
--- a/templates/edit.html
+++ b/templates/edit.html
@@ -11,7 +11,7 @@
 <meta name="robots" content="noindex,nofollow" />
 {% endblock %}
 
-{% block json_info %}<script>window.page_info={{ ( pl_js_info or {} )|tojson|safe }};</script>{% endblock %}
+{% block json_info %}<script>/*<![CDATA[*/window.page_info={{ ( pl_js_info or {} )|tojson|safe }};/*]]>*/</script>{% endblock %}
 
 {% block content %}
 
@@ -35,25 +35,32 @@
   <input type="hidden" name="csrf_token" value="{{ csrf_token() }}" />
   <div>
     <label for="title"><span class="material-icons">link</span> /</label>
-    <input type="text" name="url" class="url-input" placeholder="(No URL)" maxlength="64" value="{{ pl_url or '' }}">
+    <input type="text" name="url" class="url-input" placeholder="(No URL)" maxlength="64" value="{{ pl_url or '' }}" {% if pl_readonly %}disabled=""{% endif %}>
   </div>
   <div>
-    <input type="text" required name="title" placeholder="Title (required)" class="title-input" maxlength="256" value="{{ pl_title }}">
+    <input type="text" required name="title" placeholder="Title (required)" class="title-input" maxlength="256" value="{{ pl_title }}" {% if pl_readonly %}disabled=""{% endif %}>
   </div>
   <div id="editing-area">
+    {% if not pl_readonly %}
     <div class="pre-text-input">
       <p>This editor is using Markdown for text formatting (e.g. bold, italic, headers and tables). <a href="https://github.com/adam-p/markdown-here/wiki/Markdown-Cheatsheet" rel="nofollow">More info on Markdown</a>.</p>
-      {% if math_version %}
+      {% if math_version and pl_enablemath %}
       <p>Math with KaTeX is <mark>enabled</mark>. <a href="https://katex.org/docs/supported.html">KaTeX guide</a></p>
       {% endif %}
     </div>
     <div class="over-text-input"></div>
-    <textarea name="text" class="text-input">{{ pl_text }}</textarea>
+    {% else %}
+    <div class="pre-text-input">
+      <p>This page was locked by the owner, and is therefore not editable. You can still copy the source text.</p>
+    </div>
+    {% endif %}
+    <textarea name="text" class="text-input" {% if pl_readonly %}disabled=""{% endif %}>{{ pl_text }}</textarea>
   </div>
   <div>
     <label for="tags">Tags (comma separated):</label>
     <input type="text" name="tags" class="tags-input" placeholder="No tags" value="{{ pl_tags }}">
   </div>
+  {% if not pl_readonly %}
   <div>
     <input type="submit" value="Save" id="save-button" class="submit-primary">
     <input type="submit" name="preview" value="Preview" id="preview-button" class="submit-secondary">
@@ -63,6 +70,13 @@
     <input type="checkbox" id="CB__enablemath" name="enablemath" {% if math_version and pl_enablemath %}checked=""{% elif not math_version %}disabled=""{% endif %}>
     <label for="CB__enablemath">Enable math expressions parsing {% if not math_version %}(disabled for this instance){% endif %}</label>
   </div>
+  {% if pl_owner_is_current_user %}
+  <div>
+    <input type="checkbox" id="CB__lockpage" name="lockpage" {% if pl_is_locked %}checked=""{% endif %}>
+    <label for="CB__lockpage">Lock page for editing by other users</label>
+  </div>
+  {% endif %}
+  {% endif %}
 </form>
 {% endblock %}
 
diff --git a/templates/history.html b/templates/history.html
index 9eb6552..1ef859c 100644
--- a/templates/history.html
+++ b/templates/history.html
@@ -16,6 +16,8 @@
     #{{ rev.id }}
     &middot;
     {{ rev.pub_date.strftime("%B %-d, %Y %H:%M:%S") }}
+    by
+    {{ rev.user.username }}
   </a></li>
 {% endfor %}
 </ul>
diff --git a/templates/internalservererror.html b/templates/internalservererror.html
new file mode 100644
index 0000000..53ae91f
--- /dev/null
+++ b/templates/internalservererror.html
@@ -0,0 +1,9 @@
+{% extends "base.html" %}
+
+{% block title %}Internal Server Error - {{ app_name }}{% endblock %}
+
+{% block content %}
+<h1>Internal Server Error</h1>
+
+<p>We’re sorry, an unexpected error occurred. Try refreshing the page.</p>
+{% endblock %}
diff --git a/templates/register.html b/templates/register.html
index 4e34b07..cf6012f 100644
--- a/templates/register.html
+++ b/templates/register.html
@@ -17,18 +17,18 @@
     </div>
     <div>
         <label>{{ T('confirm-password') }}:</label>
-        <input type="password" name="confirmpassword" />
+        <input type="password" name="confirm_password" />
     </div>
     <div>
         <label>{{ T('email') }} ({{ T('optional') }}):</label>
-        <input type="email" name="email" />
+        <input type="text" name="email" />
     </div>
     <div>
         <input type="checkbox" name="legal" value="1" />
         <label>{{ T('have-read-terms').format(T('terms-of-service'), T('privacy-policy')) }}</label>
     </div>
     <div>
-        <input type="submit" value="{{ T('login') }}" />
+        <input type="submit" value="{{ T('sign-up') }}" />
     </div>
 </form>
 
diff --git a/templates/view.html b/templates/view.html
index 262c161..696ebc1 100644
--- a/templates/view.html
+++ b/templates/view.html
@@ -38,7 +38,8 @@
 <a href="/history/{{ p.id }}/">{{ T('action-history') }}</a> -
 <a href="/backlinks/{{ p.id }}/">Backlinks</a> -
 {{ T('last-changed') }} <time datetime="{{ rev.pub_date.isoformat() }}">{{ rev.pub_date.strftime('%B %-d, %Y at %H:%M:%S') }}</time> - 
-{{ T('page-id') }}: {{ p.id }}
+{{ T('page-id') }}: {{ p.id }} -
+{{ T('owner') }}: {{ p.owner.username }}
 {% endblock %}
 
 {% block scripts %}