1. A method comprising: obtaining a document for display at an electronic device, the document comprising a text content element having a font size specified in absolute value by an associated formatting directive, the font size being defined in either a body or a header of the document, and wherein the document comprises an email message; determining a count of a number of structural elements in a Document Object Model (DOM) tree structure of the document; determining that the document has a simple content layout structure based on detecting one or more indicators in the body or the header of the document, wherein one of the indicators indicates that the count of the number of structural elements in the DOM tree structure of the document is less than a threshold number; in response to determining that the document has a simple content layout structure, converting the formatting directive from an absolute value to a corresponding relative value, the relative value referencing a base value for the font size defined for the electronic device; and rendering the document for display at the electronic device using the formatting directive thus converted.