@Ortzinator Web applications do have release numbers, or at least they should have. Any site developed with even slightly more advanced release planning than directly editing the code on the production server should have some way of distinguishing different versions. However, the version number is often only used for internal purposes and is never communicated to the user. You typically don’t see a changes.txt file on most web sites.
I see a lof of people argue that the alpha and beta labels are useless with the current practice of incremental releases and frequent updates to web sites and software. Personally I think version numbers are better suited for that. For example, you could have version 1.0 alpha, 1.0 beta, 1.0 release candidate and 1.0 (final). When you add new features you go to version 1.1 alpha, 1.1 beta and 1.1 (final), and so on. If you always stay in beta and go directly from 1.0 beta to 1.1 beta, you are basically not completing the full release cycle for each update, possibly resulting in software with more features but lower quality.
I think the alpha, beta and release candidate labels still have some uses, but what they actually mean to a certain team or product may have to be defined specifically for each situation. For example, a team may decide that no new features can be added to the product after beta, or that after release candidate only bugs classified as critical will be fixed. This may or may not have any actual value to the end user.