Hud panel at spawn

Hi facepunchers!

I’ve been trying to make a 3D2D screen approx. at spawn with a browser.
The code is ready, but I am not sure where to put the lua script as this is my first script. This should be a script that is run on client when connected to the server.
The script currently resides in garrysmod/lua/autorun/client/hud.lua

My script:

local pos = Vector(0, 0, 0)
local ang = Angle(0, 270, 90)
local width = 1024
local height = 768
local scale = 0.125
local url = ""
if g_3DHTML and g_3DHTML:IsValid() then g_3DHTML:Remove() end
local browser = vgui.Create("HTML")
      g_3DHTML = browser
      browser:SetSize(width, height)
local function DrawSign()
        -- Draw a background
        surface.SetDrawColor(255, 255, 255, 255)
        surface.DrawRect(0, 0, width, height)
        -- Draw the screen
        render.DrawQuad(Vector(0, 0, 0),
                Vector(width, 0, 0),
                Vector(width, height, 0),
                Vector(0, height, 0))
hook.Add("RenderScreenspaceEffects", "3DHTMLSign", function()
     cam.Start3D(EyePos(), EyeAngles())
     cam.Start3D2D(pos, ang, scale)
     local status, err = pcall(DrawSign)
     if not status then Error(err) end

I’ve tried to run RenderScreenspaceEffects in console, but it states it as an unknown command. Could you guys please help a fellow facepuncher out?

Best regards