Twitter has two ways of identifying accounts, an @username that a user chooses and can change, and a Twitter ID that is permanent. The @username can present a problem of link rot over time as users change their handle, so sometimes linking directly to the Twitter ID is preferred.
The first step is to get the Twitter ID from the current @username. Let’s use @CNN as an example. There are a few websites that do the conversion, but these sites seem to break from time to time. One that currently works is GetTwitterID.com.
From this we can see that the @CNN account’s Twitter User ID is 759251. Now we must construct a URL using that Twitter ID, but you can’t just replace the @username in the normal URL. You have to do it in the following format:
This will direct you to a summary page for @CNN even if they change their username in the future. To link to a different account just grab the Twitter ID and replace the number in the above URL.