Answering first part of Your question: If You want to make the button more obvious, You can achieve this through css.
Open the css file and add the following classes:
.qa-nav-main-ask .qa-nav-main-link {background:#f00;}
.qa-nav-main-ask .qa-nav-main-link:hover{background:#0f6;}
.qa-nav-main-ask .qa-nav-main-selected {background:#00f;}
You can as well do this for any tab as You prefer just change ask against: activity , questions , unanswered , tag or user (taken from the url of the pages)
The upper example changes the backgroundcolor from red to green to blue.
By using position: absolute You as well can move the tabs however You want.. (May be there is a better way, but this way I am doing it.)