What is the guarantee supplied with some certificates?

The warranty aims to protect the final user. Should the Certification authority issue a certificate for a fraudulent website and should a user loose money because of the trust he placed in this certificate, then the warranty will apply. The user thought he was dealing with an authenticated entity. In that case an insurance exists to refund him up-to the maximum certificate coverage if a mistake has been committed by the Certification Authority

See the table here under to find the warranty* provided with server products.

BRAND	PRODUCT	WARRANTY
GLOBALSIGN	Extended SSL	$1 500 000
	OV Wildcard	$1 250 000
	OV	$1 250 000
	UCC	$100 000
COMODO	EV SGC	$1 750 000
	EV & EV SHA256	$1 750 000
	WildSSL & WildSSL SHA256	$250 000
	SSL & SSL SHA256	$250 000
	EV Multiple Site & EV Multiple Site SHA256	$1 750 000
	UCC & UCC SHA256	$0
	MultiWild 2+ SHA256	$0
GEOTRUST	True Business ID with EV	$1 500 000
	True Business ID with EV Multi 5+	$1 500 000
	True Business ID	$1 250 000
	True Business ID Multi 5+	$1 250 000
	True Business ID Wildcard	$1 250 000
SYMANTEC	Secure site EV	$1 750 000
	Secure site Pro EV	$1 750 000
	Secure site Pro	$1 500 000
	Secure site	$1 500 000
THAWTE	EV	$1 500 000
	Supercert	$1 250 000
	Standard	$1 250 000
	Wildcard	$1 250 000
TBS X509	Omnidomaine & Omnidomaine SHA256	$10 000
	SGC	$10 000
	Premium & Premium SHA256	$10 000
	Omnidomaine SGC	$10 000
	Ecommerce & Ecommerce SHA256	$2 500
	Standard & Standard SHA256	$50
	Multi-site & Multi-site SHA256	$0
	Intranet	$0
CERTIGNA	Certigna Signature Stamp RGS*	$0
	Certigna Timestamping Stamp RGS*	$0
	Certigna Signature Stamp RGS**	$0
	Certigna Timestamping Stamp RGS**	$0
	Certigna Code Signature Stamp RGS*	$0
	Certigna Serveur Client RGS*	$0
	Certigna SSL RGS*	$50 000
	Certigna SSL	$10 000
	Certigna SSL Wildcard	$10 000
POSITIVE SSL	Basic DV Web	$0
	Basic DV	$0
	Basic DV Wildcard	$0
	Basic DV Multiple Sites	$0
	Free DV Web	$0

*As of 2017/05/01