Nothing against grandmas or their computer skills, and yes their are many grandmas who are quite computer savvy. That said…
These are some easy design principles that I think are pretty easy. Some my fellow designer friends will think are obvious, but I’ve navigated many websites that just aren’t user friendly — even from companies that have large budgets to hire good designers.
1. Generally speaking, the navigation should be the same on every page
Same links, same colors, same location. In a book I always know where the next page is. The contents of the table of contents are always in order, nor does the table of contents move elsewhere when I come back to it.
2. Text should be BIG.
Not huge. But if you don’t think grandma can read it without a microscope, don’t put it on the page.
3. Clickable items should be easy to find
A) If it’s clickable, it should be noticeably different than other stuff.
The default for text is black and links is blue and underlined. This is what many people have come to expect. Make it clear what I can click on. To help that I suggest…
B) If it’s clickable, it should change somehow when cursor hovers over it.
Not everyone does this, but I’m a fan. If I hover over a menu item, text link, or clickable image it should change somehow. Background changes, border color changes, underline goes away, text color changes. Something like that.
4. Make it clear what to do next
When I land on a page, what am I supposed to do next? Sign up for your email list? Buy tickets? If I don’t know what the next step is or why that page exists within 3 seconds of it opening… goodbye. Tell the user what to do. Part of that is making it big. And at the top of the page. If someone doesn’t want to be told what to do, let that be their choice, not their inability to find the “buy now” link that’s tiny and at the very bottom of the page all the way to the right after some very large and unrelated images.
5. Minimize scrolling
If your header image and navigation take up half the height of the page, users probably won’t see what you really want them to do right away. I don’t care how pretty the header image is or how well you think it represents you or your company. Your losing sales because someone didn’t scroll down the 800 pixels to get to the info they were looking for. Put headlines and other general info “above the fold.”
That’s just a few I thought of off the top of my head. There’s a lot more that can be said on the topic, and an increasingly important one as the number of internet users continues to increase.