Difference between esc_url() and esc_url_raw()
From the Codex entry for Data Validation: URLs: esc_url( $url, (array) $protocols = null ) (since 2.8) Always use esc_url when sanitizing URLs (in text nodes, attribute nodes or anywhere else). Rejects URLs that do not have one of the provided whitelisted protocols (defaulting to http, https, ftp, ftps, mailto, news, irc, gopher, nntp, feed, … Read more