I never bid on projects if I am not sure on 100% that I am capable of successfully finishing the task! This is rule number one for me...
I am making web applications for more then 12 years using this skill set:
PHP5 following MVC pattern with Laravel and Phalcon,Codeigniter,Kohana
MySQL with experience in scalable projects
HTML5 mobile and desktop responsive web sites usually with Bootstrap
HTML5 advanced canvas animations
HTML5 online tools,builders