Who is the plan being written for?
A conventional debt financing lender requires less focus on some aspects than say, a potential equity stakeholding investor. It can be used solely as a marketing tool to attract interest from those who may wish to piggyback through your web presence to reach your intended market. It may just be for your own purpose to give you a heads-up, in which case the headings are perhaps just a distraction.
I mostly concur with the previous poster, putting emphasis though on understanding the context of a plan: avoid opinion unless you can substantiate your conclusions. Research is everything.
I'd also steer well clear of the "Me, me, I, I" style of pitch, or incessant repetition of your brand, company name. Lenders especially will decline if everything is dependent on you: you can get hit by a bus and then there's no business. Equally, if your marketing works, there's no infrastructure (bodies) to cope leaving you doing 80-hour weeks. Play up the management team/personnel side, even if they're outsourced and what it is they will actually have responsibility for. Keep it simple, the three key areas are: Finance, Operations, Sales. Your model should show that it's not a one-trick pony. Bolt-ons make more profit than core delivery. Can you create multiple passive income streams?
You should be able to say what you need to say, ideally clearly articulating the benefits to your web business users (and investors ROI), in less than 8-10 pages including the financials; more than that it should either be in appendices to support your assertions, or else you're waffling.
Give some thought to PEST, which is a derivative of SWOT. You have an 80% chance of something happening to you and your busines, you have little control over. The point of a plan frankly is, what is your plan B? Oh and on page one state what you're asking for, under a sub-heading: Proposal. Nothing tees off an investor more than wading through 60 pages before finding out what it is you want from them.
There's more but those are the edited highlights. Good luck!
I speak as a qualified freelance start-up business advisor and management consultant for over fifteen years...