My tool of choice for editing many kinds of files including HTML is gedit.  It is a clean and easy to use tool.  I often have to work with old html websites.  The HTML is often quite a mess with missing closing tags or just plain poorly written.  I’ve also used this to fix code I was attempting to insert into site editors using the XHTML standard.

Gedit has many plug-ins.  One of my favorites is HTML-Tidy.  This is a link to the author’s site.  Take a look and see if it helps your coding.