For people who use css with a lot of images and colors and scrollbars and whatnot - would you be okay with people skipping over your posts because they feel like they are too tedious to read? An un-css'd post shouldn't be any problem since the standard font and colors are made to be legible on the forums. Would it be rude to not force oneself to look at your customizations? I guess mostly it could harm the RP if you depend on each other's reactions...
I've only ever seen two examples on here of someone using so much CSS or poorly coordinating it that their posts were such a tedious mess to read, to the point that I lost complete interest at a glance. Those were GM posts, though. Just meant I wasn't going to consider those role-plays, frankly, if I can't even think to read the GM's posts without going through added steps. As a GM, you have to make it a point to be accessible to everyone, and that does include how you present your first post.
I actually find myself disengaged to read very long posts that are not formatted in CSS in role-plays, only because I think they are too wide on the page and stretch. A very simple div of width and activated overflow can constrain that nicely, and then it won't feel like I'm reading a never-ending report where I can see I have so much more to go and become distracted by that.
If you skip someone's player post because you're just "intimidated" by the CSS, that's your insecurity. If it's a role-play where there's hardly any interaction, whatever. But you're doing a disservice if it's an rp based in character interaction. If someone has tragically clashing text on a background color or image, why not go out of your way to ask them to adjust it? If they refuse, copy the text and plain paste it elsewhere to read. The end. CSS is just styling, you can still read the point of the post if you go out of your way to do it and not care about how it's being fronted.
But at face value--and that's
all it is because it's superficial customization of a post--if you want to use CSS, just make sure your text is
always easy to access and read. Images should be supplementary, not an overpowering focal point in the way it's arranged, especially to the point where I have to scroll past the damn thing to get to your actual text. As long as it isn't inhibiting or is in the way of your text, it's generally fine by me. Backgrounds should not clash with text nor distract the reader, but rather be an aesthetic. I use background images and font types to set a tone, and conjure an image or a feel of what my post or character is about. Be considerate of the colors you use. High contrast is used to have one thing stand out from another, and dark colors with light text makes a blessing for a long read. Too much bright and too much white can strain the eyes.
People complain about scrollbars. If there aren't so many and used arbitrarily instead of the balanced interest of space for text, it's rather whatever. If I could use webkits on these forums, I personally would have customized my scrollbars to look like those simple, fluid, contemporary iPhone ones a long time ago, because rectangular can be clunky and the look can detract.
That's my tuppence worth.