Here is a small collection of things I really think web standards are missing. I wish I had time to get involved in the W3C and suggest this, but between ocPortal and our clients, I just don't have the free time. If anybody knows if any of these are planned or wants to suggest them, let me know! I keep up-to-date with specs like HTML5 and CSS3, and a lot of things will be solved when these are finally available in browsers – so I haven't mentioned those things below.
2) I wish CSS could do simple equations like 20%+10px. Currently you need to add extra elements, and this can get very ugly and breaks the separation of concerns goal (you should not need to go and edit the XHTML to do common style changes). I don't believe CSS3 has this yet, although I could be mistaken. I do know it's a very popular request among web designers.
3) It's impossible to make truly modular CSS. You can share properties across multiple selectors, but that requires you to edit a single point of code each time, which is the anti-thesis of good engineering. Some form of OOP-style inheritance solution is needed. Again, I do know it's a very popular request among web designers.
4) Users don't trust the back button. They click it and it often asks them if they want to "resubmit a form". I propose a very simple change: include different icons for the back button, depending on whether such a message would happen or not. Of course this won't fix all the problems where developers don't use GET and POST correctly, but it's a start.
6) The XHTML 'base' tag is pretty much useless, because it breaks anchor links like '#example' (that becomes relative to the anchor, which typically ends up mapping to your index page). Let's get it fixed.
8) I wish CSS could have a property to disable margin collapsing (when the adjacent vertical margins of two boxes get merged into one continuous gap, irrespective of things like different background colours. It can lead to problems that are really hard to workaround when box backgrounds are concerned.
10) CSS needs the ability to hyphenate words if they don't fit in a box, with the feature controlled by a new property. Sometimes you have a really long word that might fit in a box in the design normally, but if the font size is made too big, it could leak out, overlaying something else (or worse, cropped, depending on overflow settings). Tabular designs don't have this problem, so let's not give people another excuse to resort to tables!
10 features that are really missing from the web - a wishlist