yunus

i consider knowledge of server caching is important thing a web developer need to know. i hardly doubt the knowledge of how browser cache is need to web developer. that's where the person comes in place called fronted developer or UI developer

i think best way to let user know about your app is by making it free and running it on beta until you have irresistible feature in the app. by then your will be having quite enough users who can signup for premium services.

even writing technical blog about how you implemented the app will drive users in for testing the app that is really great way for getting feedback and improving features.

creating plugin for popular frameworks and cms will also add a value and you will soon see users using it.

if you have enough users or customer you will soon see people getting interested in investing in the project

hope this help

i think the app is good may be a little bit of the design improvement and making the app completely free will grub some attentions. may be making it as service with apis to queue from a java scripts which can be used in static sites