Bookmarklets are one line scripts stored in the URL field of a bookmark. Bookmarklets have been around for a long time so they will work in older browsers.
You should be familiar with URL that start with schemes like
ftp, e.g. http://en.wikibooks.org/. There is also the
Using multiple lines of code 
Since you cannot have line breaks in bookmarklets you must use a semicolon at the end of each code statement instead.