I've been searching high and low for a satisfactory answer to this and failed. I hope StackOverflow can deliver for me!
I am using SharePoint Foundation 2010 (my first real attempt to deep dive into SharePoint), with (among other things) a custom web part; the master page for the site uses a CSS file supplied by the client and to which I must adhere. The issue I am having is that SharePoint, by adding several SharePoint specific CSS classes to the web part HTML structure, is conflicting with the client's styling. After some digging, I've found that the ms-WPBody class and its various element selectors are the chief culprits.
I could add !important to everything in the client style sheet, but that is verboten. I could insert some very messy styling into the child content of the web part in an attempt to override the SharePoint styling, which is the course I've been pursuing of late, but it's been getting messy. Or, I could try to remove the class from the web part, which brings me to my question:
How can I remove or otherwise override the CSS class names inserted into the HTML structuring for a SharePoint web part? I don't know enough of the inner workings of SharePoint to know what to hook to make this change, and my google-fu is fail on the subject. CssClass on the ASP.NET web control markup is obviously ignored, probably some holdover inherited from WebControl.
Help me StackOverflow! You're my only hope!
Edit
I apologize for not making it clear before, but I would like to state that I grok CSS and am not looking for help with styling. What I really am looking for is how to remove the CSS class emitted by SharePoint. Can anyone help there? I'm going to remove the CSS tag, since that appears to be confusing people. This question isn't really about CSS, it's about SharePoint.
CSS has to match the html that it is applied to - with generated html like that produced by SharePoint (or standard asp.net webforms for that matter) it is usually far easier to modify the css. If adding important is not an option you can usually do something using more specific selectors - ie a style defined as "table td" will override one for "td" though they actually select all the same elements. You can use this approach to undo any bits of sharepoint styling that are causign issues.
If you really want to change the classes sharepoint puts on the page, use jquery - trying to do that server side is really not something you want to get into on your first sharepoint project.