hmm.. since you haven’t provided a site to examine, one possibility is that the css for the plugin is being called at the wrong time.
In default themes, wp_head() is typically called just before the opening body tag… thus, any css associated with a plugin is read AFTER your style.css file
If you are defining your id or class in style.css, it may not override the default values provided by a plugin author’s style sheet.
There are three ways to address that… you *could* move wp_head() to before the call to default style sheet (not the best solution, imo) OR
write your rule in a way that gives it greater specificity AND in a way that provides the more specific values for EVERY property that has values in the plugin’s default style sheet. (the best solution, imo, since it keeps all the custom styling in YOUR style sheet)
third possibility – edit the plugin’s style sheet. If you do this, keep a backup. AND, imo, just duplicate their properties and values, comment out theirs, and edit yours. That way, if it causes problems, it is easy to go back to the originals – especially if you add notes about what and why you are doing what you are doing.
The other possible reason you may have problems… if you ARE editing the plugin’s style sheet… is that wp_head() could already be before the default style.css file in the header.php file. (Since sidebar is a selector in that style sheet, whatever is written in the plugin style sheet could be overwritten by this)
Same goes for if you have sidebar defined two places in style.css… the first instance may actually be more specific than the second..
Hard to say without being able to see your css.
HTH
um, if you don’t understand what I mean by specificity, google css+specificity. basically, the general idea with properties:values goes like this:
div.bob p.foo {
color:red;
}
p.foo {
color:blue;
}
you’d think that the last value for color would be used… however, the first rule is more specific, therefore, the second value is ignored… assuming all of your paragraphs of the class “foo” are in divs of the class “bob”
not to suggest you don’t understand this, but some might not.