Proper documentation of borrowed information helps establish your credibility and shows readers where to find your source material. Citing websites in the text can be confusing, since they sometimes lack authors and typically do not have page numbers -- two bits of information usually included in parenthetical references. In that case, you'd move on to whatever information is available to help your reader find the source of the referenced information.
Sites with an Author
The Chicago (16th edition), American Psychological Association (6th edition) and Harvard (5th edition) documentation styles have similar requirements for parenthetical references for a website with an author. In all three styles, you would give the author's last name followed by the publication date, when possible. APA puts a comma between the author's name and the publication date, while Chicago and Harvard do not. For example, in APA, such a reference might be: The company followed suit (Stannis, 2015), while Chicago and Harvard styles would require the following: The company followed suit (Stannis 2015). Both APA and Harvard require a page number, paragraph number or section title after the date to indicate the specific location of the information, when possible, while Chicago does not. For example, if the website didn't have page numbers, an example might be: Harris agrees that "fads fade" (2009, para. 3). If you are using Modern Language Association (7th edition) documentation, give the author. Include a page, paragraph or section number if the web page includes them; otherwise, leave them off: Incidents increased threefold over the month (Stannis par. 3).
Sites with No Author
For sites with no author, use the title of the page in quotation marks instead. If the title is long, just use the first few words of the title -- enough to differentiate it from your other sources. If no date appears anywhere, indicate that with "n.d." for Chicago, APA and Harvard styles, leaving out a separating comma in Chicago style. In Chicago style, you'd have: The firm opened in 2011 ("History" n.d.). APA and Harvard would add a comma, like so: The firm opened in 2011 ("History," n.d.). Since MLA style does not include dates in the parenthetical references, just give the page title in quotation marks: The firm opened in 2011 ("History"). Just as with sites with authors, you would include the page, paragraph number or section number when possible.