Now I'm no expert but this is how I fixed my Inline Label with CCK edit field issue.

In the "style.css" of my theme I entered this (use whatever settings you need, but you must float left):

label {width: 110px; float:left;}

I learned that it wasn't a class nor an id it was a "label for"... whatever that means. But it seems to work for me. And I also set the "Display Fields" to "inline" (but before placing this in the css it didn't work).

Hope this helps someone, I looked everywhere for the answer.

Comments

Your setting:
label {width: 110px; float:left;}

applies to all labels from your website, not only to CCK Form Fields.

I would like to add this to the style.css of a theme I am using, but know nothing about how to alter css code.

I tried simply tacking label {width: 110px; float:left;} to the end of the text file, but that didn't seem to have any effect. Any advice would be most appreciated.

If you are to edit an existing theme, at least copy the whole theme directory in /sites/all/themes if it is a core theme. Then each theme provides one or several css files, nested in its root directory. You just have to add or edit existing CSS properties in these files.