Q. When writing a bibliography, is it acceptable for the entry to be split between pages? Or should I insert a page break before the entry to keep it all together?
A. Please, whatever you do, do not insert a page break before the entry; if you do, then any changes you make to the document before that page break could easily result in the page just before the manual break running short. In other words, the document will no longer automatically reflow across the page break at that point. (One of a copyeditor’s many jobs is to find and eliminate such problems.)
To prevent an entry from breaking across pages, the proper way to do it is to tell your word processor to keep those lines together. First, put your cursor in the entry. Then, in Microsoft Word, go to Paragraph > Line and Page Breaks and check the box next to “Keep lines together”:
In Google Docs, the setting is under Format > Line & paragraph spacing > Keep lines together. By the way, it’s okay if a bibliography entry breaks across two pages. But note that widow/orphan control is on by default in both Word and Docs. That feature, by preventing the first or last line of a paragraph from being stranded at the bottom or top of a page, respectively, will also thereby prevent any paragraph of three lines or less—including a bibliography entry—from breaking over a page.