webpage loading.. 加载 vs 载入​​​​​​​
Strictly speaking, the word formations between 加载 and 载入 are a little different; however, as Alex has said, both are acceptable in your case.

加载(verb) = 加(verb, add) + 载(verb, load)
载入(verb) = 载(verb, load) + 入(preposition, in/into)

EDIT
Notice: both 加载 and 载入 can be used as a transitive verb or an intransitive verb.
In most cases, they are interchangeable; however, because 入 in 载入 has implied a preposition, if they are used just before a prepositional phrase, they act in different ways. For example:

These data should be loaded into the cache.

这些 数据 应当 加载 到 缓冲。

这些 数据 应当 载入 (到) 缓冲。



As 载入 has implied 入(in), the preposition 到(to) can be omitted. In contrast, if you omit 到 in the first sentence, the sentence

[Warning! May be ambiguous.] 这些数据应当加载缓冲。

is (most likely) considered as

These data should load the (contents of the) cache.

So, as you see in this 加载/载入+prepositional phrase case, they are not equivalent.