Each banner exchange network or portal has its own requirements for banners, both in standard sizes and in terms of their size in kilobytes. On this page, we tried to summarize some of the requirements that apply to standard banner sizes.
The most common sizes are the following (in pixels):
88х31, 120х60, 100х100, 200х200, 250х250, 300х250, 336х280, 240х350, 240х400, 468х60, 728х90, 120х600, 160х600
The same list, but in a more convenient form: