BuddyPress.org

I’m afraid that it’s not CSS issues you are having. Your issues are – forgive me for being blunt – a case of hopelessly mal-formed markup. The use of the general DocType used to declare an HTML5 conforming document doesn’t preclude well formed markup, at the moment it’s anyones guess as to how browsers will attempt to interpret what it has to parse as tag soup code.

Generally helping to fix up the presentational styles of a document is considered pointless with a mal-formed DOM as CSS is applied to the markup and that markup must make sense to it, the general advice is to correct and then validate the markup before troubleshooting styling aspects s often these perceived styling issues are actually corrected simply by fixing the markup.

What I can tell you is that you have clearly got mis matches between template files as I can see a padding div on ‘Gallery’ but not on ‘activity’ I can see two #containers on the activity page where only one should exist (an page or document can only declare an ID once on each page)

The other markup issues are more serious but are going to prove tricky to fix probably but they do need to be looked into you have markup elements strewn through what is the ‘head’ section of the pages with a consequence that the page body start is declared in error as it’s already open the closing head tag is redundant as it’s assumed that body has already been opened.

Sorry to be the bearer of bad news but the issue here is one of mal-formed markup firstly and secondly possibly a few elements not translated between your theme and BP when making them compatible using the theme template pack?