Let's say that you recently ran one of those PC optimizer programs. I think it's fair to expect faster boot times, and faster application load times. But, is it fair to think that your websites should load faster or have a better experience browsing the web?
One of the main limiting factors with web browsing is going to be the speed of your internet connection. While you may be able to exercise some control over the network between your PC and your router, everything else is beyond your control.
While you might get some improvement in rendering times once the data has been downloaded, you won't be able to optimise that first part of the process.
So no, it wouldn't be fair to think that websites should load faster.
Marginally / "Depends".
More memory and CPU time aren't going to affect loading of pages; bandwidth is the bottleneck.
However, if you're playing lots videos, or have multiple tabs/windows open with embedded media, it's feasible that the speed up would be more noticeable. This is especially true if you had a low amount of system memory to begin with, and after the optimisation your browser could use more memory rather than pagefile.
(Of course, if the optimising process removed applications that were using a lot of bandwidth, then yes, the difference will be very noticeable).
One thing to think about when optimizing a computer system (PC or server) is that adding more of some resource that is not the bottleneck will not resolve a performance or perceived performance problem.
For example, if the main working set that you use - the programs that you run frequently and the code for the things in those programs you regularly use - reside wholly in RAM then you will gain little or no benefit from adding RAM (could depend on your data files though and caching).
So, if you optimize your disk layout [thus get more effective bandwidth or more efficient localization of reads] and the programs you are running mostly reside in RAM (like web browsers) then you are unlikely to see performance improvements from that alone. There may be some very slight and unnoticeable improvement as browsers tend to cache to local disk but these files are (usually) extremely small.