var/mob/Loginscreen/M = usr
M << browse_rsc('web\\SplashScreen.htm',"SplashScreen.htm");
M << browse_rsc('web\\SplashScreen.png',"SplashScreen.png");
M << browse({"<meta http-equiv="Refresh" content="0; url=SplashScreen.htm">"},"window=SplashScreenBrowser");
winshow(M, "SplashScreen", "show=0")

Problem description:
What I try to do is show the SplashScreenBrowser on my default window. Inside the default window, I want it to be shown on the map called map1. How should I go about this?
You can't browse() to a map. You can put a Child in place of your map, however. Set that Child's "left" parameter to the browser(Make a new window, check it off as a pane, and put the browser in it. Click fill window then set your anchors. Make another pane and do the same thing for the map.) pane, make it do your splash screen stuff, then use winset() to set the Child's "left" parameter back to the map pane.

Use the Skin Reference and Lummox JR's Skin tutorial for more information on Childs and Panes.