Lion browser support
As of this writing, no major browsers support Lion. Chrome supported Lion until April of 2016 while Firefox supported it until August 2016. The default Safari browser hasn't been updated since 2014. Opera is built on Chrome's Chromium webkit engine so Opera support was also cut around the same time as Chrome.
Though there are "security risks" with using Lion to browse the net, I haven't had any problems. The main concern is when websites no longer support these older browsers. However, there are a few years before that will happen. Generally, software support for Lion is becoming scarce and an alternative solution will soon be necessary.
Aside from trying to install a newer version of OS X on an unsupported Mac (don't try it; it doesn't work very well), the best solution is to install an alternative operating system. Linux operating systems support the latest versions of Firefox and Chrome. Another alternative is installing Windows. Officially, the maximum Windows OS supported on MacBooks is Windows 7 x86 but I've been able to run Windows 10 x64 with a couple glitches. Two finger scrolling doesn't work and the function keys don't have the normal functions in OS X. The display brightness also can't be changed. If you don't want to pirate Windows, a digital license key can be purchased on eBay for under $10. I also highly recommend spending $10 and upgrading to 4GB of RAM to avoid using SWAP memory.
Why were many of the A1181 MacBooks dropped at Lion?
Many of the A1181 MacBooks were stuck with Lion. It's a shame Apple didn't bother rewriting x64 drivers for the graphic processors in those models as the graphic card is the only factor keeping these models from the newer operating systems. I'm a third-hand owner of MacBook 4,1 (early 2008).
A note to Apple
Please stop releasing operating systems every year and indirectly forcing users to upgrade to a new computer every few years. The new features I'll never use don't compensate for the premature loss of software support.