Many JS Warnings in FireFox?

I get alot of warnings in firefox with the new release, should I ignore it since it DO work anyway?

Warning: redeclaration of var iFrameHeight
Source File: http://admin.devocore.nu:9080/CustomMod ... ialog.html
Line: 87, Column: 7
Source Code:
var iFrameHeight = document.getElementById('frmMain').contentWindow.innerHeight ;

Warning: redeclaration of var eTabsRow
Source File: http://admin.devocore.nu:9080/CustomMod ... ialog.html
Line: 141, Column: 5
Source Code:
var eTabsRow = document.getElementById( 'TabsRow' ) ;


Warning: variable e hides argument
Source File: http://admin.devocore.nu:9080/CustomMod ... ialog.html
Line: 197, Column: 6
Source Code:
var e = e || event || this.parentWindow.event ;


Warning: anonymous function does not always return a value
Source File: http://admin.devocore.nu:9080/CustomMod ... ialog.html
Line: 204, Column: 17
Source Code:
return false ;


Warning: anonymous function does not always return a value
Source File: http://admin.devocore.nu:9080/CustomMod ... ialog.html
Line: 207, Column: 17
Source Code:
return false ;