to replace relative path with worpress path 

<img src="<?php bloginfo('template_directory'); ?>/images/mainimage.jpg" title="" alt="" />
Plugins to install

SEO admin

mobilise the blog

Next Gen gallery http://wordpress.org/extend/plugins/nextgen-gallery/

suckerfish dropdown navigation http://htmldog.com/articles/suckerfish/dropdowns/

good layout is http://www.strawberryleisure.com/