It's not hard to get an appreciation for the things designers take for granted following Tantek's experiments with undohtml.css, Eric Meyer's extended thoughts on Mozilla's default styles, and 5 minutes of poking around the web without Firefox's html.css. A look at this site conjured feelings of guilt and laziness for having not created a more explicit stylesheet, one that more accurately specifies exactly the kind of look I'm going for.
It's not as bad as it looks.
It turns out that 90% of the ugliness caused by disabling html.css (on 90% of the non-table-based sites I visited, including this one) is due to the lack of styles explicitly specifying block elements, an oversight that causes everything to appear inline. It's a mess. The following CSS mimics Mozilla's default block-level settings:
/* block elements */
html, body, div, map, dt, isindex, p, multicol,
dl, dd, ul, menu, dir, ol, blockquote, address,
center, listing, plaintext, xmp, pre, hr, marquee,
h1, h2, h3, h4, h5 {
display: block;
}The above list contains non-standard and deprecated elements, but represents the full list of Mozilla's defaults. Add/remove elements to taste. I've created a file called default.css containing these rules, which I'm now importing into this site's primary stylesheet.
I've also included Mozilla's styles for elements hidden by default, taken directly from html.css:
/* hidden elements */
area, base, basefont, head, meta, script, style, title,
noembed, noscript, param {
display: none;
}There are several other things going on in html.css, but the above styles go a long way toward getting your pages to render as expected with the default styles disabled, which at least makes it easier to see what else you've taken for granted.
Update: Eric Meyer has some additional thoughts. His minimal stylesheet includes rules for tables and lists:
li {display: list-item;}
table {display: table;}
caption {display: table-caption;}
tr {display: table-row;}
col {display: table-column;}
colgroup {display: table-column-group;}
tbody {display: table-row-group;}
thead {display: table-header-group;}
tfoot {display: table-footer-group;}
td {display: table-cell;}
th {display: table-cell;}I've moved li {display: list-item;} from my primary stylesheet, where I misplaced it before this entry, to my default.css. My current design makes no use of tables, but I've added Eric's table styles, too, just for the hell of it.