My website flashes white between page loads and is doing poorly in search engines

My website flashes white between page loads and is doing poorly in search engines References I don\'t know if my CSS code is simply in bad shape, if I\'ve done something wrong, or if I\'ve not done something that I should be doing. But my website www.calbulletbuttontool.com flashes white when navigating between pages. Additionally, it\'s doing poorly with the search engines despite every effort to have it ranked higher. I\'m so new to this I hope someone can help me in very simple terms.