how to lay out a website compatible with mobile and desktop and any browser?

[chalbri]

i recently made a websitehttp://www.albuquerqueautomotiveservice.combut i messed up big time because it fails at every mobile website tester and its just reallybadi recently learned about tablesbut then i jumped to html5 and learned about flex boxes with web kitsbut i see theyre not compatible with all browsersso im at this endless lopp of trying to find a good not perfect layout that can be viewable from any browser and any size based on what my website hasi tried google with few success and youtube is full of fake webinarsis there any one here who can lead me to finding my answer,, thank you thanks alot