You can't really modify the .a file, it contains already compiled code and symbols. You can however modify the source code and rebuild the library with whatever changes you need. Exactly how to do that will depend on what platform you're on and what changes you want to make, but downloading the source code http://www.talula.demon.co.uk/allegro/wip.html is probably the place to start.
i am using vb.net on the website there is same id textbox but when i am writing
its writen different textbox with same id "username"
<input name="username" id="username" ...