IF you are using a free theme from ANY of the repositories or private authors out there (and there are thousands) understand that they each have their own ways of dealing with CSS and page layouts. Some will conflict, some will simply behave strangely.
CSS troubleshooting has become a BIG issue on the forums, and it should not be, simply because Andy has built the forums on WordPress Standards which work well on most of the wordpress.org hosted themes.
Open Source themes are a wonderful resource for Admins and bloggers alike, however asking us to debug each and every glitch that comes along with a new theme, takes time away from developing great software.
99% of CSS conflicts can be solved by knowing a little bit about CSS tag, ID and class identifiers as well as common CSS directives such as float, align, display, etc.
There are free resources that will teach you CSS online, such as http://www.w3schools.com/ as well as other online schools. As a Wordpress plugin developer I have w3schools listed in my #1 spot of web tools as a reference resource I use all the time.
Also remember that the Theme Author is another resource of vital information regarding the theme you are using. Link Back information is generally required for free themes, and Contact information is generally supplied on the author's site.
Do not be surprised if the theme author asks for money to develop a custom theme, even if only to make an existing theme compatible with SPF. He is a theme developer. It's what he does.
All in all some small issue MAY lead to a problem deep within the SPF Core Code, however most can be repaired simply and easily with a little thought and a touch of effort.
Forums
