From the readme

Special Create Server panel Counter-Strike:Source

Post 25th August 2026 update change, the "Use Steam Networking" radio button changed.

This is a custom "Create Server" panel that alters the "Server Type" to have 4 tick boxes instead of the dropdown combobox.

The reason is to make the "Local Network (LAN) game type server the default, not the "Public (Unlisted)" one Valve made.
That way players that use CSS just for LAN games, that option does not need to be adjusted every time.

NOTE***** Just be sure you tick just ONE option not two, tickboxes work that way.

This was a request in this CSS forum item...
https://steamcommunity.com/app/240/discussions/0/580554765071608400/

You must install this in your "custom" folder e.g.:...
your drive/folder.... steamapps/common/Counter-Strike Source/cstrike/custom

************ To install ************

The folder in the download should be copied into your "Counter-Strike Source/cstrike/custom" folder.

To find that "custom" folder…
1. Open your Steam Library
2. Right-click on the “Counter-Strike Source” icon
3. Select “Manage” > “Browse local files” ….
4. A folder called “Counter-Strike Source” will pop-up
5. Open the "cstrike" folder, then the "custom" folder
6. Copy and paste the “server_gui_fix” folder in the download into “custom” folder.

The panel will change after that.
To uninstall, delete the “server_gui_fix” folder in...
your drive/folder.... steamapps/common/Counter-Strike Source/cstrike/custom

The file that was edited.

Its a custom .res file... createmultiplayergameserverpage.res
It in normally found in your drive/folder...../steamapps/common/Counter-Strike Source/hl2/resource

Edits can be read via opening the file in notepad.