In typewritten texts and other documents printed in fixed-width fonts, there is a convention among lay American English writers that two spaces are placed after the full stop (along with the other sentence enders: question mark and exclamation mark), as opposed to the single space used after other punctuation symbols. This is sometimes termed "French spacing".
In modern English-language typographical usage, debate has arisen concerning the proper number of trailing spaces after a full stop (or exclamation mark, or question mark) to separate sentences within a paragraph. Whereas two spaces are still regarded by many outside the publishing industry to be the better usage for monospace typefaces, the awkwardness that most word-processing applications have in representing correctly the 1.5 spaces that had previously become standard for typographically proportional (non-monospace) fonts has led to some confusion about how to render the space between sentences using only word-processing tools.
Many descriptivists[5] support the notion that a single space after a full stop should be considered standard because it has been the norm in mainstream publishing for many decades. This is supported by the MLA, APA[6], and The Chicago Manual of Style.[7] Many prescriptivists,[5] meanwhile, adhere to the earlier use of two spaces on typewriters to make the separation of sentences more salient than separation of elements within sentences. Since current style guides are founded on the consensus of practice, the evidence strongly suggests that most people accept the single space in modern word-processing, largely for the reason that two spaces may stretch inordinately when full justification is applied. Additionally, many computer typefaces are designed proportionately to alleviate the need for the double space (the opposition would of course reply that this does nothing to satisfy the aforementioned saliency issue). Most widely accepted contemporary style guides categorically require that only one space be placed after full stops and similar punctuation marks, and they characterise modern practice as avoiding it.[8]
With the advent of the World Wide Web, the broader distinction between full stop spacing and internal spacing in a sentence has become largely moot. Standardized HTML treats additional whitespace after the first space as immaterial (siding unquestioningly with the one-spacers), and ignores it when rendering the page. A common workaround for this is the use of character entity (non-breaking space) to represent extra spaces, and this is done automatically by some WYSIWYG editors.