Is there a way to install iPhone App via a browser (in this case iOS Safari)?
As now diawi links are only valid for a single day, I find this alternative for diawi
https://www.testgrid.io/app-deploy
It functions same as diawi. But it keeps the build on its server for 15 days. Means sharable link is valid for 15 days.
https://testflightapp.com/ is a good way to do this. It has its quirks, but overall I find it very useful.
You can use AppBox, A mac application that uses your Dropbox account to distribute you ad-hoc and enterprise apps, if you want to install form any other browser.
https://github.com/vineetchoudhary/AppBox-iOSAppsWirelessInstallation/releases
It is pretty straight forward to publish ad hoc builds on your own website. I used this tutorial to get started. http://jeffreysambells.com/posts/2010/06/22/ios-wireless-app-distribution/
Yes, safari will detect the *.ipa and will try to install it, but the ipa needs to be correctly sign and only allowed devices would be able to install it.
http://www.diawi.com is a service that will help you with this process.
All of this is for Ad-hoc distribution and not for production apps.
A new website BetaFamily has launched that allows you to generate installer link like diawi. You can also invite users and they will receive the installer link directly in their inbox. Below is the website link:
https://betafamily.com/supersend