Resolving the LOGO! Web Editor "404: The Target is Not Found" Error

The Siemens LOGO! 8 family base modules (BMs) include an integrated web server that can serve user-defined visualization pages built with the LOGO! Web Editor (LWE). When a custom page cannot be reached and the browser responds with 404: The target is not found, the fault is almost always located at the boundary between three systems: the LOGO! base module firmware, the LWE project file on the SD card, and the host browser's HTTP/HTTPS policy. This reference walks through the diagnosis, root-cause analysis, and repair of that error on a verified hardware configuration.

1. Problem Scope and Affected Hardware

The fault has been confirmed on the following Siemens order number:

Other commonly affected order numbers in the 6ED1052-1xx08-0BA0 (LOGO! 8.2 / 8.3 BM) family and the 6ED1052-1xx08-0BA1 (LOGO! 8.4 BM) family share the same web-server architecture and the same 404 symptom class. The error indicates that the BM is reachable on TCP port 80 (HTTP) but the internal web-server file index cannot resolve the requested LWE page path.

2. How the LOGO! Web Server Resolves a Page

Understanding the lookup path is essential before chasing the symptom. When a browser requests http://192.168.0.10/index.html, the LOGO! BM performs the following sequence:

1. Accepts the TCP connection on port 80 (HTTP) — failure here is a different symptom (timeout / connection refused, not 404).
2. Parses the request URI and looks for a matching resource in its internal web-server file index.
3. If a user-defined LWE project is present, the BM merges the user index with the built-in status pages.
4. Returns the matched resource, or — if nothing matches — returns HTTP 404.

Therefore a 404 means the BM is alive, the IP route is correct, the web server is enabled, but no matching file was found in the file index. The next sections identify every realistic reason this can happen.

3. Required Hardware and Software Prerequisites

Before troubleshooting, verify that the following are available:

• LOGO! Soft Comfort (LSC) version 9.x or later. From V9 onwards, the LOGO! Web Editor is integrated into LSC; no separate install is required. Refer to the official LOGO! Software overview for current versions.
• A micro-SD or SD card (verified with a 4 GB SanDisk SDHC, FAT32) inserted in the LOGO! BM.
• Ethernet connection from the host PC to the BM's RJ45 port on the same IP subnet.
• Browser with HTTP access permitted for the BM's IP address (see Section 7).

4. Root-Cause Matrix

5. Diagnostic Procedure — Step-by-Step

Execute the checks below in order; stop at the first one that fails and apply the corresponding fix.

5.1 Confirm the BM is reachable

1. From the host PC, open a command prompt.
2. Type ping <logo-ip-address> and confirm replies.
3. If the ping fails, fix the IP / subnet first. The 404 fault cannot be diagnosed without basic IP connectivity.

5.2 Open the default web page

1. Browse to http://<logo-ip-address>/.
2. If the Siemens LOGO! status page loads, the web server is alive.
3. Click every navigation link on the default page. The 404 will then reappear only on the user-defined pages — this confirms R1 (project not transferred) is the cause.

5.3 Verify the LWE project is on the SD card

1. Power down the BM and remove the SD card.
2. Insert the card into the PC using an SD adapter.
3. Open the \LOGO\ partition (the BM writes to a hidden partition the PC cannot normally see) — instead, the LWE project files are accessible from the visible root directory of the card.
4. Look for a folder named WebServer (or HTML) containing index.html and subfolders.
5. If absent, the LWE project has never been transferred to the card; re-transfer from LSC.

5.4 Verify the LWE project was downloaded to the BM

1. In LOGO! Soft Comfort, open the active LWE project.
2. Select Tools → Transfer → LOGO! Web Editor Project (or click the Web Editor toolbar → Download).
3. Confirm the target IP address matches the BM under test.
4. Wait for "Transfer complete".
5. Reboot the BM (power cycle) so the web server reloads the index.

5.5 Confirm Web Server Access is enabled

In LSC, open Tools → Ethernet Connections (or in older versions, File → Properties → Web Server Access):

• Set Web Server Access to Enabled.
• Optionally restrict by IP or set a password.
• Re-transfer the program to the BM after every change to this setting.

6. Transferring the LWE Project Correctly

The LWE project can be transferred in two ways; both must succeed for the BM to serve the page.

6.1 Transfer from the LSC Web Editor

1. Open the LSC project that contains your LWE visualization.
2. Open the Web Editor (View → Web Editor in LSC V9).
3. Build the project. The LWE produces a folder hierarchy under the project directory.
4. Use Web Editor → Download to LOGO!.

6.2 Transfer by copying to the SD card (offline method)

1. Insert the SD card into the PC.
2. From the LSC working directory, locate the generated \WebServer folder.
3. Copy it to the root of the SD card.
4. Insert the SD card into the BM and power cycle.

The second method is the "MSD card local on LOGO!" check recommended by senior forum contributors: it removes network variables from the equation and isolates the LWE project itself as the variable under test.

7. Browser-Side 404 — HTTP vs HTTPS

Modern browsers (Chrome 90+, Firefox 90+, Edge 90+) ship with HTTPS-Only Mode enabled by default or aggressive HSTS preloading. When a user types http://192.168.x.x into the address bar:

• The browser either upgrades the request to HTTPS (which the BM does not answer on port 443) and displays an error.
• Or it shows a security interstitial that, once bypassed, can produce a 404 because the secure channel never reached the BM.

7.1 Permanent fix (recommended): enable HTTP for the LOGO! subnet

1. Firefox: Settings → Privacy & Security → HTTPS-Only Mode → Enable HTTPS-Only Mode in private windows (uncheck for all windows) — or add http://192.168.0.0/16 as an exception via about:config preference dom.security.https_only_exceptions.
2. Chrome / Edge: chrome://net-internals/#hsts → enter the BM IP under Delete domain security policies. Alternatively launch Chrome with --disable-features=ChromeHttpsOnlyFirstMode (only for diagnostics).
3. Always type the BM address with the explicit scheme: http://192.168.0.10/ — do not omit the http://.

8. Network and DHCP Considerations

The LOGO! BM does not act as a DHCP client in factory state. It uses the static IP configured in LSC under IP Address / Subnet Mask / Default Gateway. If that static IP falls inside the DHCP pool of the local router, the router may at some point hand the same address to a laptop or another device, creating a duplicate-IP situation that resolves intermittently and surfaces as 404 (TCP connection to the wrong MAC) or as timeouts.

Best practice:

1. Reserve the LOGO! IP in the router (static DHCP lease tied to the BM MAC).
2. Or pick an IP outside the DHCP range, for example with DHCP pool 192.168.0.50–192.168.0.200, assign the BM 192.168.0.10.
3. Use a /24 subnet for the engineering network — anything more complex invites routing confusion that also presents as 404.

9. LWE Project File Layout and Naming Rules

The LWE generates a specific directory structure that the BM expects verbatim. Naming errors inside LWE cause the BM to silently drop the file from its index, which then triggers a 404 at request time.

10. Firmware Compatibility

The LOGO! Web Editor was introduced in LOGO! 8 firmware 8.2 and integrated natively into LOGO! Soft Comfort V9. The 6ED1052-1MD08-0BA0 BM ships with firmware 8.3.x — fully compatible.

To read the firmware from a running BM, browse to http://<ip>/ and open the Module Information page; the firmware string is reported as "FW: Vx.x.x".

11. Verification Checklist

After applying any fix, confirm success by running the following 30-second check:

1. Power cycle the BM with the SD card inserted.
2. Wait for the ETH LED to settle (solid green for 100 Mb/s, blinking for activity).
3. Browse to http://<ip>/.
4. The Siemens default page loads.
5. Navigate to your custom LWE entry page (typically http://<ip>/index.html).
6. The page renders without 404 and live tags (I0, I1, M1, VW0 …) update when the LOGO! program toggles inputs.

12. Field-Proven Repair Sequence (Quick Reference)

1. Check the SD card: present, FAT32, ≤ 32 GB, working in a PC card reader.
2. Re-transfer the LWE project from LSC → Web Editor → Download to LOGO!.
3. Verify Web Server Access = Enabled in LSC.
4. Confirm the BM's IP is outside the DHCP range and reserved in the router.
5. Disable HTTPS-only mode for the engineering subnet in the browser.
6. Hard-reload the page (Ctrl + F5) to bypass browser cache.
7. If the 404 persists, transfer the project by SD card and reboot the BM.
8. If still failing, clear the SD card, reformat as FAT32, and re-transfer.

13. Extended Diagnostic — Reading the BM Web-Server File Index

Advanced users can interrogate the BM's internal index by querying the diagnostic page (available on FW 8.3 and above):

• http://<ip>/logo\_diag.shtm — diagnostic overview, lists firmware, memory card presence, and web-server status.
• http://<ip>/logo\_websrv.shtm — lists every web-server resource the BM has loaded.

If the LWE folder appears in the diagnostic listing, the BM has the project; if not, the transfer or SD-card path is broken.

14. Frequently Encountered Edge Cases

Symptom: Custom page works in LSC simulation but 404 on the real BM.
Cause: LWE was never downloaded to the BM; only the LSC project was. Solution: Web Editor → Download to LOGO!.

Symptom: Page loads once after power-up, then 404 on next browser refresh.
Cause: SD card write-protect switch engaged. Solution: slide the lock on the SD adapter.

Symptom: 404 only when accessing from a smartphone on the same Wi-Fi.
Cause: Mobile browser HSTS preloading more aggressive than desktop. Solution: navigate to http://<ip> explicitly with the scheme, or use a browser that allows per-network HTTPS exceptions.

Symptom: Intermittent 404 while the LOGO! program is running.
Cause: LWE variable names exceeding 16 characters or containing reserved tokens. Solution: shorten tag names to match LSC symbol table conventions.

15. FAQ