A contract except a few can be made orally. Writing is not the essential element. A web-site offering sale of chattels such as books, ornaments, computers etc need not concern about the requirement of writing and signature. However, in the eyes of common law signature is by nature a means to authenticate a person's identity and hence ensuring that the party's identity is not easily denied. In Goodman v J Eban Ltd  1 All ER 763, it was held that “The essential requirement of signing is the affixing, either by writing with a pen or pencil or by otherwise impressing on the document, one's name or “signature” so as to personally authenticate the document”.
There exists no decided cases in common law that the typed signature or scanned signature contained in an email is legally equivalent to a hard-written signature. However, Goodman seems to suggest that in so far as a “thing” is sufficient for the sake of authenticating a person, it amounts to “signature”. Digital signatures have formally ascribed through the Electronic Transactions Ordinance to become a “signature”. Therefore, digital signatures are given their “signature” status by legislative intervention and hence the function of authenticating a person. However, it must be noted that digital signature having the effect equal to manual signature must a recognized one issued by a certification authority recognized under the Electronic Transaction Ordinance. These include the Postmaster General of HKSAR Government and Digi-Sign. Widely known certification authorities such as Verisign may not have been recognized under the Ordinance and hence the status of digital signatures issued by them are still governed by the common law.