TheMadScientist - 6:21 pm on Nov 2, 2012 (gmt 0)
The URL needs to stay the same for search engine purposes and page request tracking to start build a URL list, etc ... That's what the example I gave does.
The line of Mod_Rewrite tells the server to get the page /serve-503-error.php and serve it to any URL a visitor requests. You definitely Do Not want to redirect anything anywhere or you'll likely just be causing more issues down the road.
Basically, you want to keep any visitor on the URL they requested and 'take the information to the visitor' (rewrite) rather than moving the visitor to a different URL or 'taking the visitor to the information' (redirect).