Many instructors are accustomed to preparing course lessons just a few hours, days, or weeks in advance of teaching the lessons. That approach is not successful with web courses. The e-Learning Center strongly recommends that you develop the entire course well in advance of when you plan to teach it. Even if you're creating a web-enhanced course, your students will appreciate it if you put course documents, such as the syllabus or assignment directions or online readings, into the web course at the outset of the course.
Of course, you are free to modify the course as you're teaching it. If you find that something isn't working well for your students, you can change it on the fly as the course progresses provided you have mastered the necessary technical skills and you communicate clearly with your students about what types of changes you are implementing and why. Keep in mind that students sometimes print course web pages at the beginning of the course. If you later change your web pages during the course, you need to tell your students so they don't refer to the earlier printouts.